RoleAccessControlHandler.php

<?php

namespace Drupal\user;

use Drupal\Core\Access\AccessResult;
use Drupal\Core\Entity\EntityAccessControlHandler;
use Drupal\Core\Entity\EntityInterface;
use Drupal\Core\Session\AccountInterface;

/**
 * Defines the access control handler for the user role entity type.
 *
 * @see \Drupal\user\Entity\Role
 */
class RoleAccessControlHandler extends EntityAccessControlHandler {
    
    /**
     * {@inheritdoc}
     */
    protected function checkAccess(EntityInterface $entity, $operation, AccountInterface $account) {
        switch ($operation) {
            case 'delete':
                if ($entity->id() == RoleInterface::ANONYMOUS_ID || $entity->id() == RoleInterface::AUTHENTICATED_ID) {
                    return AccessResult::forbidden();
                }
            default:
                return parent::checkAccess($entity, $operation, $account);
        }
    }

}