I created a prototype last night to sweep up the frisbee. This was using a 3/8" piece of plywood with about a 1/8" gap under the plywood. The frisbee would pretty consistently pop up onto the ramp.
There are 2 small wheels by the front edge. The idea being that those wheels will keep it from catching on the bump in the carpet. This also had 2 castors on the back edge of the ramp putting it about 4" off the ground.
http://www.youtube.com/watch?v=M7JbdU4h6F8