diff --git a/application/models/Roles_model.php b/application/models/Roles_model.php
index ff8b25da..8b5f8005 100644
--- a/application/models/Roles_model.php
+++ b/application/models/Roles_model.php
@@ -12,75 +12,314 @@
  * ---------------------------------------------------------------------------- */
 
 /**
- * Roles Model
+ * Roles model
+ *
+ * Handles all the database operations of the role resource.
  *
  * @package Models
  */
 class Roles_model extends EA_Model {
     /**
-     * Get the record id of a particular role.
+     * Save (insert or update) a role.
      *
-     * @param string $role_slug The selected role slug. Slugs are defined in the "application/config/constants.php" file.
+     * @param array $role Associative array with the role data.
      *
-     * @return int Returns the database id of the roles record.
+     * @return int Returns the role ID.
+     *
+     * @throws InvalidArgumentException
      */
-    public function get_role_id($role_slug)
+    public function save(array $role): int
     {
-        return $this->db->get_where('roles', ['slug' => $role_slug])->row()->id;
+        $this->validate($role);
+
+        if (empty($role['id']))
+        {
+            return $this->insert($role);
+        }
+        else
+        {
+            return $this->update($role);
+        }
     }
 
     /**
-     * Returns all the privileges (bool values) of a role slug.
+     * Validate the role data.
      *
-     * The privilege numbers are converted into bool values of the four main actions (view, add, edit, delete). By
-     * checking each value you can know if the user is able to perform this action.
+     * @param array $role Associative array with the role data.
      *
-     * @param string $slug The role slug.
-     *
-     * @return array Returns the privilege value.
+     * @throws InvalidArgumentException
      */
-    public function get_privileges($slug)
+    public function validate(array $role): void
     {
-        $privileges = $this->db->get_where('roles', ['slug' => $slug])->row_array();
-        unset($privileges['id'], $privileges['name'], $privileges['slug'], $privileges['is_admin']);
-
-        // Convert the int values to bool so that is easier to check whether a user has the required privileges for a
-        // specific action.
-        foreach ($privileges as &$value)
+        // If a role ID is provided then check whether the record really exists in the database.
+        if ( ! empty($role['id']))
         {
-            $privileges_number = $value;
+            $count = $this->db->get_where('roles', ['id' => $role['id']])->num_rows();
 
-            $value = [
+            if ( ! $count)
+            {
+                throw new InvalidArgumentException('The provided role ID does not exist in the database: ' . $role['id']);
+            }
+        }
+
+        // Make sure all required fields are provided.
+        if (
+            empty($role['name'])
+        )
+        {
+            throw new InvalidArgumentException('Not all required fields are provided: ' . print_r($role, TRUE));
+        }
+    }
+
+    /**
+     * Insert a new role into the database.
+     *
+     * @param array $role Associative array with the role data.
+     *
+     * @return int Returns the role ID.
+     *
+     * @throws RuntimeException
+     */
+    protected function insert(array $role): int
+    {
+        if ( ! $this->db->insert('roles', $role))
+        {
+            throw new RuntimeException('Could not insert role.');
+        }
+
+        return $this->db->insert_id();
+    }
+
+    /**
+     * Update an existing role.
+     *
+     * @param array $role Associative array with the role data.
+     *
+     * @return int Returns the role ID.
+     *
+     * @throws RuntimeException
+     */
+    protected function update(array $role): int
+    {
+        if ( ! $this->db->update('roles', $role, ['id' => $role['id']]))
+        {
+            throw new RuntimeException('Could not update role.');
+        }
+
+        return $role['id'];
+    }
+
+    /**
+     * Remove an existing role from the database.
+     *
+     * @param int $role_id Role ID.
+     *
+     * @throws RuntimeException
+     */
+    public function delete(int $role_id): void
+    {
+        if ( ! $this->db->delete('roles', ['id' => $role_id]))
+        {
+            throw new RuntimeException('Could not delete role.');
+        }
+    }
+
+    /**
+     * Get a specific role from the database.
+     *
+     * @param int $role_id The ID of the record to be returned.
+     *
+     * @return array Returns an array with the role data.
+     *
+     * @throws InvalidArgumentException
+     */
+    public function find(int $role_id): array
+    {
+        if ( ! $this->db->get_where('roles', ['id' => $role_id])->num_rows())
+        {
+            throw new InvalidArgumentException('The provided role ID was not found in the database: ' . $role_id);
+        }
+
+        return $this->db->get_where('roles', ['id' => $role_id])->row_array();
+    }
+
+    /**
+     * Get a specific field value from the database.
+     *
+     * @param int $role_id Role ID.
+     * @param string $field Name of the value to be returned.
+     *
+     * @return string Returns the selected role value from the database.
+     *
+     * @throws InvalidArgumentException
+     */
+    public function value(int $role_id, string $field): string
+    {
+        if (empty($field))
+        {
+            throw new InvalidArgumentException('The field argument is cannot be empty.');
+        }
+
+        if (empty($role_id))
+        {
+            throw new InvalidArgumentException('The role ID argument cannot be empty.');
+        }
+
+        // Check whether the role exists.
+        $query = $this->db->get_where('roles', ['id' => $role_id]);
+
+        if ( ! $query->num_rows())
+        {
+            throw new InvalidArgumentException('The provided role ID was not found in the database: ' . $role_id);
+        }
+
+        // Check if the required field is part of the role data.
+        $role = $query->row_array();
+
+        if ( ! array_key_exists($field, $role))
+        {
+            throw new InvalidArgumentException('The requested field was not found in the role data: ' . $field);
+        }
+
+        return $role[$field];
+    }
+
+    /**
+     * Get all roles that match the provided criteria.
+     *
+     * @param array|string $where Where conditions
+     * @param int|null $limit Record limit.
+     * @param int|null $offset Record offset.
+     * @param string|null $order_by Order by.
+     *
+     * @return array Returns an array of roles.
+     */
+    public function get($where = NULL, int $limit = NULL, int $offset = NULL, string $order_by = NULL): array
+    {
+        if ($where !== NULL)
+        {
+            $this->db->where($where);
+        }
+
+        if ($order_by !== NULL)
+        {
+            $this->db->order_by($order_by);
+        }
+
+        return $this->db->get('roles', $limit, $offset)->result_array();
+    }
+
+    /**
+     * Get the permissions array by role slug.
+     *
+     * The permission numbers are converted into boolean values of the four main actions:
+     *
+     * - view
+     * - add
+     * - edit
+     * - delete
+     *
+     * After checking each individual value, you can make sure if the user is able to perform each action or not.
+     *
+     * @param string $slug Role slug.
+     *
+     * @return array Returns the permissions value.
+     */
+    public function get_permissions_by_slug(string $slug): array
+    {
+        $role = $this->db->get_where('roles', ['slug' => $slug])->row_array();
+
+        unset(
+            $role['id'],
+            $role['name'],
+            $role['slug'],
+            $role['is_admin']
+        );
+
+        // Convert the integer values to boolean.
+
+        $permissions = [];
+
+        foreach ($role as $resource => $value)
+        {
+            $permissions[$resource] = [
                 'view' => FALSE,
                 'add' => FALSE,
                 'edit' => FALSE,
                 'delete' => FALSE
             ];
 
-            if ($privileges_number > 0)
+            if ($value > 0)
             {
-                if ((int)($privileges_number / PRIV_DELETE) == 1)
+                if ((int)($value / PRIV_DELETE) === 1)
                 {
-                    $value['delete'] = TRUE;
-                    $privileges_number -= PRIV_DELETE;
+                    $permissions[$resource]['delete'] = TRUE;
+                    $value -= PRIV_DELETE;
                 }
 
-                if ((int)($privileges_number / PRIV_EDIT) == 1)
+                if ((int)($value / PRIV_EDIT) === 1)
                 {
-                    $value['edit'] = TRUE;
-                    $privileges_number -= PRIV_EDIT;
+                    $permissions[$resource]['edit'] = TRUE;
+                    $value -= PRIV_EDIT;
                 }
 
-                if ((int)($privileges_number / PRIV_ADD) == 1)
+                if ((int)($value / PRIV_ADD) === 1)
                 {
-                    $value['add'] = TRUE;
-                    $privileges_number -= PRIV_ADD;
+                    $permissions[$resource]['add'] = TRUE;
                 }
 
-                $value['view'] = TRUE;
+                $permissions[$resource]['view'] = TRUE;
             }
         }
 
-        return $privileges;
+        return $permissions;
+    }
+
+    /**
+     * Get the query builder interface, configured for use with the roles table.
+     *
+     * @return CI_DB_query_builder
+     */
+    public function query(): CI_DB_query_builder
+    {
+        return $this->db->from('roles');
+    }
+
+    /**
+     * Search roles by the provided keyword.
+     *
+     * @param string $keyword Search keyword.
+     * @param int|null $limit Record limit.
+     * @param int|null $offset Record offset.
+     * @param string|null $order_by Order by.
+     *
+     * @return array Returns an array of roles.
+     */
+    public function search(string $keyword, int $limit = NULL, int $offset = NULL, string $order_by = NULL): array
+    {
+        return $this
+            ->db
+            ->select()
+            ->from('roles')
+            ->like('name', $keyword)
+            ->or_like('slug', $keyword)
+            ->limit($limit)
+            ->offset($offset)
+            ->order_by($order_by)
+            ->get()
+            ->result_array();
+    }
+
+    /**
+     * Attach related resources to a role.
+     *
+     * @param array $role Associative array with the role data.
+     * @param array $resources Resource names to be attached.
+     *
+     * @throws InvalidArgumentException
+     */
+    public function attach(array &$role, array $resources): void
+    {
+        // Roles do not currently have any related resources. 
     }
 }