I dislike rollers, because if you don't have them perfectly in-line/perpendicular, they can skew the direction.
The exception is bearing ball roller stands. But they're a pain IMO (boards with any bowing downward will have a higher chance of catching on something.
Here's an overview:
http://www.rockler.com/blog/index.cfm?mode=entry&entry=7F493116-1372-6771-F6AE41A8DE4FE9FB
I've used several different types, and roller ball stands.
These aren't rollers.. but these are my favorites. I have two and have used them now for 4+ years.
http://www.homedepot.com/h_d1/N-5yc1v/R-100618242/h_d2/ProductDisplay?catalogId=10053&langId=-1&keyword=ridgid+support&storeId=10051
I use them with my tablesaw, bandsaw (when resawing), router table, and even with the MFT.