Hey Steve, I never thought of using a roller to float a ceiling. I've always done it the hard way.
The only concern I have here is the amount of additional weight that is going to be added to the ceiling. Personally, I'd start by driving screws into the ceiling to support the extra weight and be certain the the screw heads don't break the paper surface of the drywall. A pair of drywall screws ever foot or so will suffice. I'd then suggest that you try to keep your coats as thin as possible.