I've seen worse. This roller may be able to be rejuvenated. My method is to scrub with naptha and a cotton swab, which is only done during overhauls, as naptha is fairly aggressive and a little too strong for regular maintenance, where I use denatured alcohol. Extreme case may require a light sanding to get through the old rubber layer, and if you are at that point, replacement is usually desirable. But if replacements cannot be sourced easily or cheaply, the sandpaper may mean the difference between working and not.
Removing rollers are done by driving the pin out with a punch on a block of wood. Only one side of the pin is captive, the other side is free. You want to drive the pin out with the captive side on top, thus you only have to move the pin about 1mm before it is free to move. If you try and drive it out from the free side, you will be fighting the metal cage/arm grip all the way through and likely ruin the cage. I don't remember which side is captive and which is free but if you look closely while squeezing the two sides of the arm with your fingers, you can usually see one side is moving relative to the pin and the other side is not.
