I live in the same metro area as Rock Island Auction and know the President Kevin Hogan.
They do an excellent job on Collectible Colts and antiques, not so well on more modern or not widely known guns like Rohrbaughs. I have never seen a Rohrbaugh on their auction.
Again, 17% seller's fee and 15% buyer's premium, gets the price up their in a hurry. I have bought quite a few Auto Mags from them and I flip them to people I know or on GunBroker for good profits.
Personally, I would take my chances on GunBroker first. JMO