1. Season meat and bones of rib roast with salt. Rub mustard all over meat and sprinkle with rosemary and pepper. Place roast, rib-side down on a baking sheet. Transfer to refrigerator uncovered or loosely covered for 1 to 3 days; remove roast from refrigerator 3 hours prior to roasting.

2. Preheat oven to 450 degrees with a rack set in the bottom third.

3. Place roast rib-side down in a roasting pan just large enough to fit the roast (about 12 by 14 inches). Transfer roast to oven and position pan so that the bone ends are facing the oven door. Roast until outside begins to brown and sizzle, about 20 minutes.

4. Reduce oven temperature to 325. Do not open oven. Cook until an instant-read thermometer inserted into the thickest part of the roast reaches 110 to 115 for rare, 120 degrees for medium-rare, and 125 degrees for medium, about 1 1/2 hours. If meat has not reached desired degree of doneness, cook 10 to 15 minutes more. Once roast reaches 95 degrees, the temperature should rise 8 to 10 degrees more for every additional 10 minutes cooked.

5. Transfer roast to a carving board; let stand 25 to 40 minutes, loosely covered if desired. If you plan to make Yorkshire pudding, pour beef drippings into a glass measuring cup and set aside, along with the hot roasting pan. Cut strings and remove bones. Slice meat across the grain into 1/4- to 1/2-inch-thick slices and transfer to a warm serving platter. Pour any drippings from carving over meat and serve.