Roast Beef with Horseradish Ranch Dressing Sandwich

4 large Kaiser rolls or hard rolls
12 ounces shaved Aries Beef Roast Beef
8 thin slices red onion
8 slices ripe tomato
2 cups shredded lettuce

Horseradish Ranch Dressing:
1 cup ranch style salad dressing
8 teaspoons prepared horseradish
4 teaspoons parsley, finely chopped
4 teaspoons sweet red pepper, finely chopped optional

1 pound Aries Beef thinly sliced cooked roast beef, cut into 1-inch strips (3 cups) 6 burger buns, split

In 1-quart saucepan, heat all sauce ingredients to boiling over medium heat, stirring constantly; reduce heat.
Simmer uncovered 10 minutes, stirring occasionally. Stir beef into sauce.
Cover and simmer about 5 minutes or until beef is hot.
Fill buns with beef mixture.