Rocs are giant birds. No, I'm not going to come up with any witticisms for the overgrown songbird.
They have 18 animal HD. I encourage you to try and remember when the phrase '18 animal HD' was ever followed by a LA of +0 or more. Sure, rocs are strong and tough, but their fly speed is so-so, they don't have any natural ability to wield weapons or use objects, and they just plain don't have anything that makes them worth playing.