A friend at work had an old drawer with a broken runner wheel. The manufacturer no longer makes them. What a perfect situation for a 3D printer! I modeled the existing wheel in Autodesk's 123D Design using nothing but cylinders of various sizes, using the Combine/Merge and Combine/Subtract tools. I chamfered the edges of the wheel, but realized after printing the first prototype it wasn't enough, so added more and the second prototype looked good. I added the screw pocked on one side so when screwed to the bracket, the head will have some recessed room to hide in.

The wheel measures 28.2mm in diameter, with a 7mm hole in the center. The projection on the side is 5.26mm. I'm including the 123D file in case anyone else needs to modify this to suit their application.