A ribeye steak is essentially a prime rib roast, cut between the ribs into individual steaks.  A roast is slowly cooked in the oven, while steak is typically pan-fried, grilled, or broiled. Many people actually prefer to buy whole boneless roasts and cut them into individual steaks. Costco has great roasts, by the way, and if you do it this way, you could save quite a bit.