1/3 cup finely ground coffee
2 tablespoons kosher salt
1 tablespoon freshly ground black pepper
1/4 vanilla bean, split and seeds scraped
One 12-pound, bone-in prime rib roast (5 bones)
In a bowl, thoroughly blend the coffee with the salt, pepper and vanilla bean seeds. Set the rib roast in a roasting pan and rub it all over with the coffee mixture, concentrating most of the rub on the fatty part of the meat. Turn the roast bone side down and let stand at room temperature for 30 minutes.
Preheat the oven to 450°. Roast the meat for 15 minutes. Reduce the oven temperature to 325° and roast for about 2 1/2 hours longer, until an instant-read thermometer inserted in the thickest part of the meat registers 125° for medium-rare.
Transfer the roast to a carving board and let rest for 20 minutes. Scrape off any excess coffee rub. Carve the meat in 1/2-inch-thick slices and serve.
Make Ahead: The coffee-rubbed roast can be refrigerated overnight. Bring to room temperature before roasting.