Stand roast, fat side up, on a rack in a shallow pan. Add no water. Insert roast-meat thermometer into center of roast, making sure point rests on meat, not in or on fat, gristle or bone.
Roast uncovered in a slow oven (300 to 325°) until thermometer registers the doneness you like (140° for rare, 160° for medium and 170° for well-done meat), about 23 to 25 minut