Preheat oven to 200°C. Tie the beef at regular intervals with unwaxed white kitchen string to secure. Reserve 3 whole sprigs of rosemary. Coarsely chop 1 tablespoon of the remaining rosemary. Combine the chopped rosemary, oil and garlic in a small bowl. Rub the rosemary mixture over the beef. Thread the reserved rosemary sprigs under the string on the beef. Season with salt and pepper.
Heat the extra oil in a roasting pan over high heat. Add the beef and cook, turning occasionally, for 6 minutes or until brown all over. Roast in the oven, basting regularly with pan juices, for 15-20 minutes for medium-rare or until cooked to your liking.
Remove beef from baking pan and transfer to a plate. Cover with foil and set aside for 10-15 minutes to rest. Remove string and rosemary sprigs from the beef. Carve the beef across the grain into thick slices. Place on a serving platter and serve immediately with horseradish or your preferred gravy or sauce, and fresh seasonal vegetables.