Preheat the oven to 500 degrees F. Put the roast on a flat surface and season all sides with salt and pepper, to taste, and put it on a roasting rack. Arrange the potatoes in the bottom of the roasting pan and season them with salt and pepper, to taste. Put the rack in the pan directly over the potatoes.
Put the pan in the center of the oven and roast, undisturbed for 10 minutes. Lower the temperature to 350 degrees F. Count about 10 minutes for each pound then begin testing the internal temperature. An instant-read thermometer should register about 130 degrees F for medium-rare. Remember that "carry over" cooking (when the roast comes out of the oven and rests) will mean the temperature will increase. Transfer the roast to a platter and serve with the potatoes.