If you need to replace the roller, it is far easier to grind off the welds on the outside of the plates.  It is welded only on the outer surface of the metal plate.  (Been there, done that!)

Then you can replace the pin with a bolt and nyloc nut of suitable size, or have a new pin welded in place if you believe that is superior.

Bill Kinney
Harmonie, SM160
Annapolis, MD