Bring the roast to room temperature about 30 minutes before cooking. Combine the mustard, grated garlic, and the horseradish together in a small bowl and brush over the roast. Season all over with salt and pepper and place on the rack of a roasting pan.
In the bottom of the roasting pan add in the onions, garlic, carrots, parsnips, and potatoes. Add in the bay leaf, rosemary, 1 tablespoon of the olive oil and season with salt and pepper. Toss to coat the veggies in olive oil. Place the rack over the veggies and drizzle the remaining olive oil over the roast.
Place into the oven and cook for 15 minutes then reduce the heat to 350 and add the beef stock to the bottom of the pan with the vegetables. Cook the roast for an additional 1 hour or until the internal temperature reads 125 for medium rare. Remove from the roast form the oven and let rest for 15 minutes before thinly slicing. Serve with the vegetables.
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