Combine salt & pepper in a small bowl. Pat the roast dry with paper towels and rub with the salt/pepper mixture. Wrap kitchen twine twice around the widest part of the roast and tie it tightly. Refrigerate the roast, uncovered, at least 6 hours and up to 24 hours.
When ready to cook, remove the roast from the fridge 30-60 minutes before cooking. Set oven rack to lower-middle position and heat oven to 450°F. Line a baking sheet with foil and spray a metal baking rack with nonstick spray. Set the rack over the baking sheet.
Transfer the roast to the metal rack and brush with 4 tablespoons butter.
Roast the meat until the internal temperature registers 110°F on an instant-read food thermometer, about 1 hour.
While the roast cooks, prepare the glaze (see below).
Once the internal temperature of the roast registers 110°F remove the roast from the oven, and reduce the oven temperature to 325°F. Brush the entire roast with the glaze. Return the roast to the oven and cook, basting every 15 minutes with the glaze, until the internal temperature registers 140°F-145°F on the thermometer, about 1 hour. (Start checking the temperature of the roast after 45 minutes.).
Transfer the roast to a carving board and brush with the glaze. Tent the roast loosely with sprayed foil. Allow the roast to rest 20-30 minutes before slicing.
A few minutes before serving, reheat the glaze (on the stovetop or in the microwave).
Remove the twine from the roast and slice it between the bones. Transfer meat to a serving platter and drizzle with extra glaze.