yii\rbac\BaseManager::getRole PHP Method

    public function getRole($name)
    {
        $item = $this->getItem($name);
        return $item instanceof Item && $item->type == Item::TYPE_ROLE ? $item : null;
    }

 /**
  * Fill relations between roles and permissions
  */
 protected function fillChildren()
 {
     foreach ($this->getConfig('children') as $roleName => $permissionsNames) {
         $role = $this->authManager->getRole($roleName);
         foreach ($permissionsNames as $permissionName) {
             $permission = $this->authManager->getPermission($permissionName);
             if (!$this->authManager->hasChild($role, $permission)) {
                 $this->authManager->addChild($role, $permission);
             }
         }
     }
 }