Does it have something to do with the corkscrews?
Also, a few interesting bits I noticed: Rolling doesn't speed you up in this game. It doesn't slow you down, either, but you don't accelerate when rolling. Essentially, the speed you were going when you began to roll is the speed you stick at. You can go much faster by continuing to run.
And there are a bunch of slopes which you cannot roll on unless you enter them rolling. Namely any curved surface.
Just thought I'd like to share.