Yes, the 9100 has a rubber roller, and yes it turns to goo.
As Katie said, the original roller had a flat on it, but it's possible to use a circular roller, it's just a little harder to push the cards in. I've repaired both my 9100Bs that way -- AFAIK the 9100B mechanism is identical to that in the A (although the PCB is different, I think).
My method for replacing it involves dismantling the reader, taking off the old roller (I made a special puller tool for this), then turning a new hub from 7/8" brass rod, pressing it in place in a vice (vise to you, I guess :-)), and fitting a 1" O/D O-ring.
I believe (if you can find a suitable adhesive), you can stick such an O-ring (the standard size is 1" O/D, 3/4" I/D and therefore 1/8" thick) onto the orignial metal hub. Worth a try if you don't have access to a machine shop :-)