Preheat oven to 325 degree F. Place roast on a rack in a shallow baking pan. Combine walnuts and snipped rosemary; press over top and sides of roast. Sprinkle with salt and pepper. Roast for 1-1/4 to 1-1/2 hours or until internal temperature reaches 160 degree F and juices run clear.
Meanwhile, in a small saucepan combine remaining ingredients. Bring to boiling. Reduce heat. Boil gently, uncovered, about 15 minutes or until sauce is reduced to 1 cup. Allow sauce to cool 15 minutes. Remove rosemary sprig. (Sauce thickens slightly as it cools.) Spoon sauce over slices of pork roast. Pass remaining sauce. Makes 8 servings.