Print N and P Wheel Hub's as many as you need.
Print R (roller) - will print 6 Rollers, each takes eleven rollers.

Roller Preperation:
Trim any Ozebane and maybe sand the "top" side of the roller to make it flat and smooth.

HUB preperation:
Remove any Ozebane and other dimpled in the wheelspaces.

Fixing rollers in HUB:
Use small pcs (approx 10 mm) of 3 MM filament as axels.
Remenber to add rubber rim (O-rings, like farnell 185-2406)
uk.farnell.com/lapp-kabel/53102020/o-ring-m20-2-0mm-pk25/dp/1852406?Ntt=1852406
Naturally the size of the O-ring is importan - you can get O-rings many places.
The axels are glued into the sockets with some ABS dissolved in Acetone

--- my nxt mindstorm has only 3 motors, and you need 4 to drive the wheels in any direction....

--- Can somebody please make a Gearbox for 4 mechanum wheels.
there are 6 gearstick postions:
Forward
Reverse
Right
Left
Rotate right
Rotate left