Hmm, I don't know what to tell you. I've pulled ubercart beta-2 out of the box off of d.o and I installed it, created a few roles, created a new product that assigns roles, and when I set the order status to completed all roles were assigned. The bug you have sounds definitely like the one mentioned in the link, however that should have been nailed. Is your test server out on the net? If so, you can PM about a way to access your site. I would definitely be interested in seeing what's going on there, but with out all the details it will be tough to see what's going on.