I've had my rock bass for 5 years or so now (look at avatar). I caught it as a little two inch juvenile and kept him in a 29g with some other natives including a longear sunfish. For food he initially ate things like blood worms, beef heart and bits of worms and things. I eventually got him taking pellets but he would only take softer pellets at first, like HBH Super Soft. Eventually I got him to take regular cichlid pellets.
He has had a number of tank mates over the years ranging from native sunfish to convicts and severums and has never been particularly aggressive but can hold his own. Currently he lives in a 75g with other sunnies including a green and they all get along fine. He does fine at room temp and enjoys having cover such as driftwood. He is about 8" in length.
He is one of my favorite fish, tons of personality, hardy and pretty to look at. They're worth giving a try, good luck if you get one.