Roomba Front Caster Wheel
Based in concept only from the wheel by thingibox, however when I used that wheel the Roomba could not dock and charge. After a bit of investigation, the other wheel sat a little high and prevented the Roomba from docking.
This wheel sits a little lower and allows the Roomba to dock successfully.
I have completely redesigned this rather than using the thingibox file, since I am really bad with Sketchup.