Preheat oven to 400 degrees.
Wrap the roast beef deli slices in foil. Using two foil packs will heat the meat up quickest.
Place the deli meat in oven for 15 minutes.
As the deli meat warms up in the oven, place the Ricos Premium Cheddar Cheese Sauce in a saucepan on a low-medium heat on the stovetop. Stir frequently for 10 minutes.
Assemble the sandwiches. Place a teaspoon of horseradish on each bottom hamburger bun, followed by four slices roast beef deli meat, then a dollop of the Ricos Premium Cheddar Cheese Sauce.
Complete with the top of the hamburger bun and serve.