I'm using a Dax Friction Drive and the steel roller that came with the kit (1.25). I haven't made any home-made rollers yet because I don't have a drill press. I tried making cut-outs from a plastic board, but the results weren't good.
I think if you have a drill press you can make the accurate center hole and cut-out shape. For locking it to a Dax driveshaft, you can drill a couple holes in the sides, just wide enough to hammer a nut in there sideways, then before the nut, drill through the roller so the set screw can go through to the driveshaft. You could even counter drill the set screw holes and use allen cap screws.
I think if you have a drill press you can make the accurate center hole and cut-out shape. For locking it to a Dax driveshaft, you can drill a couple holes in the sides, just wide enough to hammer a nut in there sideways, then before the nut, drill through the roller so the set screw can go through to the driveshaft. You could even counter drill the set screw holes and use allen cap screws.