The roller part is broken

We don't sell a roller that matches what you show here, unfortunately. It's tough to be sure, but it looks like your housing had a mounting tab that broke off at the back. Can you confirm? Or is it supposed to just be a little edge like that?

A couple rollers you could consider are our 81-085, or maybe even our 81-294. However their designs are very different compared to yours and there is no guarantee they will work. 

I am sorry that we couldn't offer you anything better.