A rib-eye roast is a large, boneless cut of meat that is taken from the rib section of the animal, while prime rib is a cut taken from a rib roast. The rib roast differs from the rib-eye roast in that the rib roast contains two or more rib bones.
The rib roast can also be referred to as a prime rib roast because of the prime rib meat cuts that come from it. There is also a slight difference in the area of the animal that a rib-eye and a prime rib roast, and therefore prime rib, comes from. The rib-eye and prime rib roast are both cut from a pair of muscles that run parallel to the spine, from the neck of the animal to the hip, but the rib-eye roast is generally taken from the muscles that are closer the neck, while the prime rib roast is cut from anywhere between the sixth and the 12th rib of the animal.
The other difference between a rib-eye roast and a cut of prime rib is the way they are cooked. Rib-eye roast is generally placed on a roasting rack and cooked in an oven that is set to 350 degrees Fahrenheit. A cut of prime rib is generally pan fried or grilled.