dont use rollers, way too expensive.
just build a wooden ladder out of two 10' 4x4s with 2x4 ladder steps, then wrap astroturf around the steps and staple / nail it to the back. you get so much more speed and there is no need for soap, water, or snow gel. its also a ton lighter and you can walk back up the drop in ramp or even sidestep up it with your skis on.
if you dont understand i can draw up a diagram.