Heh, good stuff, overcoming the ol' demon of riding friction drives in the wet goes on, lol. Problem is it's just going against the mechanics of friction to lubricate it as is the case with a tire picking up water. A little more down pressure on the roller and a light touch feathering the throttle helps, but hills and acceleration become problematic.
Living in a place where it rains a lot, I've tried many. Steel in any config, fluted, knurled, smooth, slip when wet for the same reason you squirt a little water under a handlebar grip to get it off. Wood, smooth or slotted will slip. Polyvinyl rollers slip. The most practical I think is the rubber idea and about the best traction, rubber on rubber, and it doesn't over wear the tire.
I tried going with more aggressive surfaces, and increased the tire wear especially if you leave them on for very long when the roads dry. I've tried the sanding belts, emory cloth lasted longer, the paper backed fell apart pretty quick but neither lasted very long. Tried mixing paste epoxy with new aquarium sand and coating a steel roller with it, worked pretty good but still slipped riding in rain though it is a halfway decent solution to building up a worn roller. About the best aggressive roller for non-slip was aggregate stone grinding wheels, something about their porosity that water doesn't inhibit or cause them to slip. Of course, they are the most abusive of all on tires.
left to right: 3 wood, 1 polyvinyl, 2 stone
I do think the rubber on rubber is about the best, and the idea of quick change rollers is a plus. That and pick your weather as best you can, lol.