Gordie, do you own any drift pins? If you do, that can be used to help remove the clamp pin. Or, you could find a nail the same size as the roller pin. If you use the nail cut the pointed tip off, that way the nail won't mushroom the end of the roller pin. If you want to try using the nail, you could drill a hole just a bit larger than the roller pin in a piece of wood for the opposing side. Take the block of wood, and hold it tight up against one side of the clamp over the roller pin. Then on the opposite side, use the nail and hammer the roller pin into the hole in the block of wood. You might need another person to give you a hand doing this. If you do it right it will work, I've done this in the past.
Len