Two hours before roasting, remove meat from frig and allow it to come to room temperature. Place oven rack on 2nd lowest position. Preheat oven to 500 degrees. Be sure your oven is very clean before heating to 500 to reduce smoking.
Place roast in pan large enough to hold it comfortably, bone-side down, and spread the top thickly with the salt and pepper. Roast meat for 45 minutes. Without removing the meat from the oven, reduce the oven temperature to 325 degrees F and roast for anouther 30 minutes. Finally, increase the temperature to 450 degrees F and roast for another 15-30 minutes, until internal temperature of the meat is 125 degrees F. Be sure thermometer is exactly in the center of the roast. The total cooking time will be between 1 1/2 and 1 3/4 hours. Meanwhile, make the sauce.
Remove the roast from the oven and transfer it to a cutting board. Cover tightly with aluminum foil and allow to rest for 20 minutes. Carve and serve with Mustard Horseradish Sauce or Stilton Sauce.