12 pounds Prime Rib roast, at room temperature
Salt and freshly ground pepper, to taste
Preheat oven to 425 degrees.
Season roast with salt and pepper. In a roasting pan place roast, fat side up, so that ribs of roast act as rack. Roast for 30 minutes and reduce heat to 350 degrees. Continue to roast for 2 hours more or until meat thermometer registers desired doneness. Transfer to platter and let rest, covered, for 20 minutes.
For the pan sauce:
2 cups beef stock or canned broth Sprig of thyme or 1/2 teaspoon dried Worcestershire sauce, to taste Salt and freshly ground pepper, to taste
Skim off fat from pan drippings and add stock and thyme. Bring to a boil and simmer 10 minutes. Season with Worcestershire and salt and pepper to taste. Transfer to a sauceboat.