Pending status by default for a specific role

The following code can go in the functions.php file of your theme. However, this kind of operation should not really be bound to a theme. Changing themes would allow the users with your specific role to publish again. Therefore, just put the code in simple plugin.

<?php
/**
 * Plugin Name: My specific roles and capabilities
 * Plugin URI:  http://wordpress.stackexchange.com/questions/71841/pending-status-by-default-for-a-specific-role/71843
 */

$role = get_role('specific-role'); // Pick your role

if ( ! empty($role))
{
    $role->remove_cap('publish_posts');
}

See codex: get_role() and publish_posts.