Place a flat, oiled rack inside a lightly oiled shallow roasting pan or casserole dish. Set aside. Remove roast from the refrigerator at least an hour before positioning rack in the middle of the oven and preheating to 250 degrees.

If needed, trim fat to about 1/2-inch thickness. Using a sharp knife, separate the roast from the bones by cutting closely along the bones. Season roast with salt and pepper to taste everywhere except the side where the bones were cut away. Place a skillet just large enough to hold the roast over high heat. When the skillet is hot, add the roast, upside down, and sear until nicely browned, about 8 to 10 minutes. Also brown both ends and along the curved portion, but do not sear the unseasoned, bone side.

Reposition roast back onto the bone; firmly secure with butcher's twine, but not too tightly. Place roast - bone side down -onto the prepared rack inside the roasting pan.

Cook until a meat thermometer (placed into the thickest portion of the meat) registers 120 degrees for rare or 125 degrees for medium-rare, about 3 to 3 1/2 hours. Cook longer for well done, if desired.

Allow roast to sit at least 30 minutes. Cut the butcher twine, lift the roast off the bones, slice and serve. Return the bones to the oven to roast longer if needed.