Preheat your oven to 350°F (175°C).
Slice the slider buns in half horizontally.
Place the bottom halves of the buns in a baking dish.
Layer the sliced roast beef evenly over the buns.
Sprinkle shredded cheddar cheese on top of the roast beef.
In a small bowl, mix mayonnaise and horseradish sauce.
Spread the sauce mixture over the cheese layer.
Add sliced pickles and tomatoes on top.
Place the top halves of the buns over the fillings.
Bake in the oven for about 10 minutes or until the cheese is melted.