Heat oven to 350 °F. Prepare the ingredients for the paste rub by combining oil, garlic and pepper together in a bowl.
Rub the beef roast generously with salt on all sides. Press marinade evenly onto the beef roast.
Place beef roast in a baking pan with the fat side up. Insert an ovenproof meat thermometer into the thickest part of the beef, making sure it's not touching the bone. Roast for about 2 1/2 hours. Refer to doneness temperature in blog post notes above.
Prepare the ingredients for the horseradish sauce. Peel and grate the horseradish, finely dice fennel bulb and chop fresh fennel fronds.
Whisk whipped cream until you get soft peaks. Add in horseradish, fennel bulb and fennel fronds. Season with salt.
Place the sauce in a refrigerator until ready to serve.
Serving Rib Roast with Horseradish Sauce
Once the roast is removed from the oven, lightly cover it with foil and let it rest for at least 15 minutes. Serve it with your favorite sides.