1 bone-in beef rib roast, about 19–20 pounds
2 tablespoons chopped rosemary
4 tablespoons kosher salt, divided
1 teaspoon pepper
1 tablespoon chopped garlic
1⁄2 cup finely grated fresh horseradish
2 cups sour cream
1 tablespoon minced chives
1 teaspoon white wine vinegar
1 teaspoon salt
Dash hot red pepper sauce
Rib Roast: If refrigerator space is available, place roast, uncovered, on a rack over a sheet pan and allow to “air dry” for 3 days. Remove roast 2 hours before roasting.
Mix the rosemary, 1 tablespoon salt, pepper, and garlic together in a small bowl; set aside. Using a sharp knife, slice the bones away from the roast about 3⁄4 of the way down, creating a pocket. Rub the rosemary mixture into the pocket. With butcher’s twine, tie the bones back to the roast between each rib. Rub the remaining salt all over the roast. Place the rib roast on its side on a “V” rack in a roasting pan and then tent with foil. Roast for 30 minutes with the ribs closest to the fire.
Remove pan from oven and carefully roll the roast so the fat side is up. Return to the oven and roast, rotating the pan every 30 minutes for about 3 1⁄2 hours, or until the internal temperature in the center of the roast reaches 120° F. Remove from the oven and let rest 30 minutes, covered.
(Larger cuts of meat need more resting time to redistribute their juices, and the internal temperature will increase more than a smaller cut of meat.)
To serve, remove the bones from the roast and slice.
Horseradish Sauce: Combine all ingredients in a bowl and mix well. Chill well before serving.