[Zope] accessing users by role

I have an application with many user-defined security roles. I'd like to display a drop down with users that have a certain role. Is there an easy way to "get a list of users with role X"?

From what I can tell you can only start with a user and see what roles they have. That would be a lot of work to build this dropdown. I'm looking for a quicker way.

any ideas? thanks! -Kevin