Roles fieldset

Great little module for easy reordering of registration fieldsets. I was looking through the forums for ages for something like this, and glad to find your offering.
The module has picked up my custom profile fieldsets without any problem, and a newsletter fieldset too. But the Roles fieldset is the one I really want to move to the top of my registration page, and it's not displaying on the weights list. And weight changes to the generic looking "account", "locale", "submit", appear to do nothing. Any suggestions? Thanks.