The Ring Roller we have in the Theatre Metalworkshop is used mainly by Costume students for making crinolines, paniers, corset boning and headresses etc.
I made it by adapting a large metalworking bench vice. The vice jaws were removed and replaced with two heavy gauge pieces of steel angle which carry the rollers mounted on top (as shown in the image below).
Closing the vice with the vice handle applies the pressure to the steel, which will be rolled between the rollers.
In all honesty the large bench vice was a little over-kill as the rollers aren’t able to cope with anything more than 5-6mm o/d steel. However, it works really well and is always being used.