01 - Preheat oven to 400°F. Line a baking sheet with parchment paper to prevent sticking during baking.
02 - Melt butter with olive oil in a skillet over medium heat. Add sliced onions and cook, stirring occasionally, until golden and caramelized, about 8-10 minutes. Season with salt, pepper, garlic powder, and thyme.
03 - Lay tortillas flat on a clean surface. On each tortilla, layer sliced roast beef, caramelized onions, and one slice of provolone cheese, distributing evenly.
04 - Tightly roll up each tortilla and place seam-side down on the prepared baking sheet. Optionally, brush tops lightly with olive oil for enhanced crispness.
05 - Bake for 10-12 minutes until tortillas are golden and crisp, and cheese has fully melted. Monitor closely to prevent over-browning.
06 - While roll ups bake, combine beef broth, Worcestershire sauce, soy sauce, onion powder, and garlic powder in a small saucepan. Bring to a simmer over medium heat and cook for 5-7 minutes to meld flavors. Adjust seasoning as needed.
07 - Remove roll ups from oven and allow to cool slightly. Slice each roll in half diagonally if desired. Serve immediately with warm au jus for dipping.