did you see the Beijing Olympics opening? They used a cylinder that moved across the filed and it left behind a long piece of paper. The cylinder was not actually moving but the image that was displayed on the scroll was animated to roll.
Not easy to do in Motion but think in terms of three separate projects. The first one reveals your base layer, the sheet of paper, with a mask. The second produces a cylinder with a moving surface. The third marries them together. Sync up the simulated cylinder with the movement of the mask.
Faking a cylinder in Motion is really difficult. Best I can come up with is a combination of Fun House and Scrape. There are probably some 3rd party filters for Motion that include cylinders, Boris, for instance and a fabulous cylinder for AE.
Hoe you get better advice soon.
This is my standard sigfile so do not take it personally: "For crying out loud, read the freakin' manual."