Prepare the au jus according to the package instructions. Side Note: If you have the time to make homemade au jus–click this link for instructions.
Toast the slider buns by preheating the oven to broil. Place the opened slider buns on a baking sheet.
Place in the oven and cook, watching carefully, for a few minutes, or until the buns are golden & toasted. Remove from the oven.
Prepare the French dip sliders by placing the thinly sliced roast beef slices into the HOT au jus for a few seconds to warm up, then place on the bottom buns.
Add a tomato slice on top of the meat, then season with sea salt and freshly cracked pepper, to taste, followed by some provolone cheese.
Spread some cream horseradish sauce on the top buns, if desired.
Finish the sliders by placing them back under the broiler for a few minutes or until the cheese is melted.