I used a Harbor Frieght pipe threader to power my rock sifter. Its output is 40rpm which I would think ideal for a bead roller. I don't have a bead roller yet.

I've been contemplating using it to power my HFT ring roller, just haven't gotten back to using the roller so not gotten around to using the threader on it yet. I got my threader out of the HFT return bin for I think $100. It's got plenty of oomph and could power my rock sifter just fine. The cool thing about it is the quick connect style dies make it quickly transferable between machines.