A buddy of mine tried the roller blade wheels. They work awesome for sliding the ski, but they actually wore through the paint over time. Each wheel had quite a bit of pressure as compared to spreading the pressure out over a whole bunk. The paint wore out right where the wheels touched, so he had a bunch of bald spots on his hull.
I used these bunk slides.
http://www.surfixinc.com/surfix_trailer_bunkslides.html They are a pretty soft plastic. I think they are pretty nice to the hull, but mine is already messed up so it's hard to tell. The slides make unloading and loading way easier. I can push and pull the ski off the trailer with one hand. My only complaint is that I didn't get them sooner.