Slice roll in half. Evenly distribute roast beef on bottom half. Drizzle salad dressing (recipe below) over beef. Layer with onions, tomatoes and lettuce. Cover with roll top and secure with toothpick.
In a small bowl, combine all ingredients. Set aside.
Nutrition Information Per Serving: 430 calories, 14g fat, 40mg cholesterol, 1040mg sodium, 50g carbohydrate, 3g dietary fiber, 26g protein.