customizable roller bearing

There are a couple of roller bearing models; with this one you can customize the dimensions in OpenSCAD.

Customizing:

Download OpenSCAD (open source; Win/Mac/Linux), load the scad file and use the customizer on the right to change dimensions and tolerance.

Printing: 

I recommend random seams and 3 perimeter walls. Otherwise 0.4mm nozzle and 0.17mm layer height (0.2 should be ok, too). For bigger bearings I'd use more walls and more sparse infill (like 30% gyroid).