Remove prime rib from refrigerator and allow the meat to come to room temperature, about 3 hours depending on the size of the roast.
Preheat oven to 425 degrees F (220 degrees C). Line a roasting pan with aluminum foil.
Unwrap the roast and place onto roasting pan; blot with paper towels. Sift together flour, pepper, salt, paprika, onion powder, garlic powder, and celery seed into a small bowl. Coat the roast all over with the flour mixture.
Roast in preheated oven until cooked to your desired degree of doneness; about 4 1/2 hours (20 minutes a pound) for medium-rare. Roast to an internal temperature of 120 degrees F (49 degrees C) for medium-rare; 130 degrees F (54 degrees C) for medium; or 140 degrees F (60 degrees C) for well done.
When the roast has finished cooking, take it out of the oven, and cover with aluminum foil. Allow to rest in a warm spot for 30 minutes to 1 hour before slicing.
