Preheat oven to 375 degrees F (190 degrees C). Place a rack inside a roasting pan.
Mix garlic powder, onion powder, dill weed, pepper, and salt together in a bowl; rub onto roast, including the ribs. Place roast, rib-side down, onto rack in roasting pan.
Bake roast in the preheated oven for 45 minutes. Turn off oven, keeping the door closed the entire time, and keep roast in oven for 3 hours. Turn oven back to 375 degrees F (190 degrees C) and cook roast until an internal temperature of 145 degrees F (65 degrees C) is reached, 30 minutes more.