Used to be able to buy tiny bottles of "Rubber Drive Cleaner"(White label, blue letters?), which cleaned beautifully AND softened-up "hardening" rollers, as well. Though after use I used to go over the rollers with a bit of alcohol, to remove the - rather oily - cleaner itself. Worked great!
Years after I'd used my last reel-to-reel, I pulled the last few drops out of an old bottle in a last-ditch effort to "restore" the hard-as-a-rock, rubber roller on a pin printer. Came up just like new and worked fine 'til I went ink jet, a couple of years later.
Teddy G.