[Zope] Registering people in CMF as "Guests"

I have a couple of CMF sites and really love it (reeeeeeeeally I do), but I have a new project where I need to have people be able to register as a "Guest" (different role) or as a "Member" (the role register does now). I poked around some of the scripts but I cannot seem to find anything that shows me what role they get out of the box or where to change that. Anyone done this? Probably something darn simple I am missing. Thanks, BZ