I'm looking at buying a few. If they are just regular, old piano rolls, how much is a fair price to pay for them? The player doesn't yet work, so I don't want to go nuts, buying hundred of them. I just want to get a few.

You should be able to acquire piano rolls for about $1-$5 per title at estate sales, indoor flea markets, etc. New ones cost more like $15-$20 each.

The titles that fetch the highest prices on the resale market are newer-vintage QRS rolls. They are also the best as they adapted a lot of pop songs from the 1950s-1990s for piano roll. Also considered valuable are reproducing rolls for AMPICO, Duo-Art, and Welte-Mignon, but those rolls are of no use unless you have a compatible player piano.

Anything else besides these is going to be cheap and readily available.

There are also lots of eBay auctions for piano rolls, if you don't find any in your local market. If your player isn't working, I'd say to just get a few cheap old rolls that are still intact and hang onto them to test your piano. Then, once you are enjoying your restored player piano, you'll probably want to get as many QRSs as you can get your hands on.

Depends. Nobody's interested in a box of forgettable off-Broadway showtunes from the '20s that closed after a week, but stuff played by the actual composer and rolls for reproducing pianos and nickelodeons can fetch quite a bit, although still probably in the $5-$20 range. Definitely stay away from Elektra rolls and other cheap brands, because they used an extremely acidic paper that's really brittle and yellowed today. Also, stay as far away as possible from "coon" songs and minstrel rolls, unless you want something that's so racist it'll make a redneck blush.