yii\rbac\DbManager::removeAllPermissions PHP Method

    public function removeAllPermissions()
    {
        $this->removeAllItems(Item::TYPE_PERMISSION);
    }

 public function actionRemoveAllRoles()
 {
     if ($this->confirm('Are you sure want to remove all roles? All parent child relations will be adjusted accordingly.')) {
         $this->_authManager->removeAllPermissions();
     }
     return 0;
 }