I made my own rollers a few years back. Made them out of 3/4" thick hard maple, glued together. They started out at nearly 5" diameter, but due to they varying density (and weight) of each board, balancing them was nearly impossible. They spin at something like 40 revolutions per second!
I turned them down to 3 1/2" diameter and balanced them with no more vibration or bounce.
Here's a picture:
http://i655.photobucket.com/albums/u...amibay/003.jpg