Preheat oven to 350°F.
Coat 9 x 13-inch baking dish with cooking spray. Cut rolls in half, horizontally. Place bottom half in prepare baking dish; spread horseradish on cut side. Top with Deli Roast Beef and cheese. Close sandwiches. Using a paring knife, cut into 12 sandwiches.
Combine butter, Worcestershire sauce, parsley, sugar and onion powder in small bowl; mix to combine. Pour butter mixture evenly over prepared sandwiches. Cover and refrigerate 1 hour to overnight.
Bake sandwiches, uncovered, in 350°F oven 15 to 20 minutes or until cheese is melted and rolls are golden brown.
Nutrition information per serving: 453 Calories; 164.7 kcal Calories from fat; 18.3 g Total Fat; 9 g Saturated Fat; 3.7 g Trans Fat; 1 g Polyunsaturated Fat; 3.7 g Monounsaturated Fat; 86 mg Cholesterol; 426 mg Sodium; 51 g Total Carbohydrate; 2.8 g Dietary Fiber; 21 g Protein; 3.5 mg Iron; 182 mg Potassium; 3.5 mg Niacin; 0.1 mg Vitamin B6; 0.4 mcg Vitamin B12; 1.2 mg Zinc; 9.8 mcg Selenium; 16.3 mg Choline;