Best way to update all role IDs on existing site?

Thanks for this much-needed module. I have a multisite with a large number of sites, all with the same roles. I want to enable role export on all these sites (in preparation for exporting some rules that rely on role ID), and at the same time update all of the existing role IDs to use the hash generated by role export. Can you recommend the best way to do this? I found that I was able to run this php script via drush for each role and it seems to work, but I'm not sure if there's a better way:

<?php
$role = user_role_load_by_name('administrator');
role_export_user_role_update($role);
?>

This would be pretty easy to run against all my sites if it's an acceptable solution.

Thanks in advance.