[JesseK]

I'm curious as to what the actual wheel & roller supports are made out of.

It LOOKS like it's a VEX gear with machined supports(?), which could give a performance degrading flaw: Most of the mass of the wheel is on the outside and will therefore take alot of torque to overcome inertia, relative to if most of the wheel mass is around the axle. If the center is machined VEX metal, then you won't see this performance hit so much.

Looks like it would get the best traction out of all of the VEX mecanum designs I've seen though. Excellent idea for the roller hubs.