Combine the ketchup, water, onion powder, garlic powder, Worcestershire sauce, salt, and apple cider vinegar in a small bowl. Stir to combine. Set aside.
Arby’s Cheese Sauce
Heat the Cheez Whiz, milk, and shredded cheddar cheese in a small saucepan on low heat until the cheese has melted. Reduce heat to a simmer.
Roast Beef Sandwich
Layer slices of roast beef in a nonstick skillet.
Sdd 1 tablespoon of water. Place the lid on the skillet. Turn the heat to medium and allow the beef to steam for 3 to 4 minutes.
In the meantime, slice the onion buns if necessary
Butter the inside of the buns, and toast in a hot skillet.
Build the sandwich by spreading about 1 tablespoon of Arby’s Red Ranch Sauce on the bottom bun. Add 1/4 of the roast beef to each sandwich, and top with Arby’s Cheese Sauce. Cover the sandwich with the top bun.