@basicxman yes but if you find a way to make them out of vex parts please provide instructions, what would you use for rollers? to get the 45 degree angle?
to make the rollers I think I would use the half inch spacers. They are quite big, not the black ones you get in the starter kit.
they are from the spacer kit on this page:
http://www.vexlabs.com/vex-robotics-fasteners.shtml
as to create the angles I think either custom cutting the metal plates or over lapping the metal bars and bending them...
There are a few pictures in the gallery that are made out of what I just described I believe.
You would think that you could just use omni wheels... aren't they the same thing? just build differently? They are made to allow all directions of movement, same thing with the mecanum wheels right?
edit: YES! The one's the otherguy posted we're EXACTLY what I was talking about.