Prep the onions (optional): Heat olive oil in a skillet over medium heat. Add sliced onion, a pinch of salt, and cook for 6–8 minutes until soft and lightly golden.
Set aside.
Make the garlic butter: In a small bowl, combine melted butter, minced garlic, Italian seasoning, black pepper, and a pinch of salt. Stir well.
Warm the au jus: In a small pot, add beef broth, Worcestershire, soy (if using), onion powder, garlic powder, and thyme. Bring to a simmer for 5 minutes.
Taste and adjust seasoning. Keep warm on low.
Assemble the roll ups: Lay a tortilla flat. Add a line of roast beef across the lower third, top with some sautéed onions (if using), and a generous layer of cheese.
Don’t overstuff—leave 1 inch at the edges.
Roll tightly: Fold the sides inward slightly, then roll from the bottom up into a snug log. Repeat with remaining tortillas.
Brush with garlic butter: Lightly brush the outside of each roll up with the garlic-butter mixture. This helps crisp and flavor the tortillas.
Crisp in a skillet: Heat a large nonstick skillet over medium heat with a thin film of oil or cooking spray.
Place roll ups seam-side down. Cook 2–3 minutes per side, turning to brown all around, until golden and the cheese is melted.
Serve: Slice in half if you like, and serve hot with warm au jus on the side for dipping.