how are you creating the roles ? and how stored in the db ?
are you using http://codex.wordpress.org/Function_Reference/add_role ?
are they additional roles (ie each person has more than one)?
Is problem replicated with normal roles ? if so, try reinstalling the code etc (I have no such problems on my various test systems, so there must be something different or odd about your setup)
if you think there is nothing unusual about your role setup then:
if you like you may email me a sql dump of your users, usermeta tables and possibly wp_options table and I'll see if I can recreate the problem. I may charge a small fee to advise you what the solution is if it is NOT a plugin problem.
If it is a bug, I will fix it, no charge of course.
Alternatively see http://wpusersplugin.com/support/. Paid support starts in 1/2 hr increments.