Heat oven to 375°F (190°C) and grease a baking dish.
Lay tortillas flat and evenly layer roast beef and cheese.
Tightly roll up tortillas and place seam-side down in baking dish.
Mix melted butter, garlic powder, and onion powder; brush over tops.
Bake for 18–22 minutes until golden and melted.
Make au jus according to packet directions with 2 cups water.
Slice roll ups and serve warm with au jus for dipping.
