1. Preheat your oven to 400F
2. Wrap the roast beef slices in tin foil and place in the oven to warm for 15 minutes
3. Add half a container of cheese whiz to a small bowl and place in the microwave for 30 seconds until melted.
4. Lightly toast buns until golden brown and begin assembling the sandwiches.
5. Place 1 tsp. of horseradish on each bottom hamburger bun, followed by four slices of beef deli meat and add a spoonful of cheese whiz. Place hamburger bun on top and serve.