1. Place meat, fat side up, in a 15-1/2x10-1/2x2-inch roasting pan. Insert a meat thermometer into center of meat. In a large bowl combine horseradish, olive oil, pepper, the 1 teaspoon thyme, and the salt. Spoon half of the mixture over beef. Set remaining horseradish mixture aside. Roast beef in a 350 degree F oven for 30 minutes.
2. Meanwhile, peel a strip from the center of each potato; cut larger potatoes in half. Toss potatoes and carrots with reserved horseradish mixture. Arrange vegetables in pan around roast. Roast 1-1/4 to 1-1/2 hours more or until the thermometer registers 145 degree F for medium-rare, stirring vegetables once. Remove from pan. Cover with foil. Let stand 15 minutes before carving meat. (The meat's temperature will rise 5 degrees during standing.)
3. For sauce, add wine to roasting pan and stir up the brown bits. In a medium saucepan stir the 1-1/4 cups broth into the flour and 1/4 teaspoon thyme until smooth. Stir in wine from roasting pan. Cook and stir until thickened and bubbly; cook and stir 1 minute more. Serve sauce with meat and vegetables. If desired, garnish wtih fresh thyme sprigs. Makes 8 to 10 servings.