Do you mean the type where both spools are on one side and the film takes a long tight path across the pressure plate? I think these were only made to slide in under 4x5 groundglass backs. It can't be made small enough to slide in under a 2x3 groundglass back.

The usual rollfilm backs attach with the Graflok mechanism, which, unfortunately is not present on the back of your camera. Here is a thread dealing with a Bushman to Graflok conversion, do some searching, as there are other ways to get a rollfilm back on that camera, but it may not be easy:
http://www.apug.org/forums/forum147/...ressman-c.html