What is the difference between Prime Rib and a Standing Rib Roast? (and a "rib eye roast" while you're at it)
Prime rib can be either a steak sliced from the roast or the entire roast. In other words, it isn't a precise term.
The standing rib roast is more precise. You can get more than one prime rib steak from the standing rib roast. The standing rib roast must have come from at least 2 of the ribs.
A rib eye roast is a standing rib roast with the ribs removed.
The prime rib (standing rib roast or steak cut from that area) is actually not required to be USDA prime beef.