One restaurant I worked in specialized in prime rib. We would regularly roast four rib loins in a day, and during the tourist season, we would keep eight loins cooking literally around the clock. We’d cook the loins to rare, and since the carving station was set up under a heat lamp next to the grill, on busy nights the meat would continue to cook. We often had to rotate the rib sections on and off the carving board. If someone ordered prime rib well done—and, yes, such people do exist in this world—we’d drop a cut into the well of au jus we kept at the grill station until meat was grey and the tip and cap had peeled away from the eye. Smart guests who wanted a slice on the done side ordered an end piece.
Our menu called this beef dish prime rib, but we rarely used USDA Prime beef. We most often used a Choice rather than the much more expensive Prime grade, but rib roast is usually called prime on menus because it is, after all, from one of the eight primal cuts in a steer (brisket, shank, rib, loin, round, chuck, flank, and plate). Most of the beef you find in supermarkets is Choice or Prime; check the label. Ribeye steaks are simply uncooked slices of a rib roast. Roasts with bones are usually known as bone-in or standing rib roasts; a ribeye steak with a bone is often called a tomahawk.
You can bet a rib roast can be expensive, usually from $7 to as much as $27+ per pound; the average is around $15-20. The price can be much cheaper during the major holidays, around $8 to $12 per pound. Bone-in roasts usually have three to seven ribs and are slightly cheaper. Each rib slice, on average, can generate enough meat for two larger slices. A three-rib roast can feed about seven people; figure 16 ounces of uncooked boneless roast per person.
At the restaurant, we would first wipe down the whole boneless rib loins (each easily weighing 15-20 lbs.) with a clean, moistened cotton cloth, then coat the entire slab of meat heavily with coarse sea salt, then place them directly on the racks in an oven set at 250. We’d check the loins every half hour or so with a meat thermometer, removing them when they were very rare (@ 120). Those we didn’t use were refrigerated for heating later.
For an evenly-cooked, succulent 7 lb. rib roast, preheat the oven to 475. Pat the roast dry, coat with sea salt and minced garlic, and place on a on a rack in a pan. If you’re using a bone-in roast, you can simply rest the meat on the bones. Cover with a cloth and bring to room temperature. When you place the roast in the oven, wait a half hour, then turn the heat down to 275. In an hour, begin checking with a thermometer. When you get a 125 reading in the thickest part of the roast, immediately remove the meat from the oven, and let rest about five minutes a pound before carving and serving. Dredge individual slices in hot au jus to desired doneness for individual guests. Serve with a ramekin of au jus, a good brown mustard, and freshly-grated horseradish.