role management for custom record action

Hi,

I created a custom action for a custom module, but i need restrict the access to this action if the current user is in a specific role. How can i do that?

<?php
array (
  'type' => 'actiondropdown',
  'name' => 'main_dropdown',
  'primary' => true,
  'showOn' => 'view',
  'buttons' => 
    array (
      0 => 
      array (
        'type' => 'rowaction',
        'event' => 'button:edit_button:click',
        'name' => 'edit_button',
        'label' => 'LBL_EDIT_BUTTON_LABEL',
        'acl_action' => 'edit',
      ),
      1 => 
      array (
        'type' => 'rowaction',
        'event' => 'button:custom_action:click',
        'name' => 'custom_action',
        'label' => 'LBL_CUSTOM_ACTION',
        'acl_action' => 'view',
      ),
      2 => 
      array (
        'type' => 'pdfaction',
        'name' => 'download-pdf',
        'label' => 'LBL_PDF_VIEW',
        'action' => 'download',
        'acl_action' => 'view',
      ),
?>

Thanks for the help