01 - Preheat oven to 375°F. Line a baking sheet with parchment paper.
02 - Heat 1 tbsp butter in a small pan over medium heat. Add onion and sauté 3–4 minutes until tender. Add garlic, half the black pepper, and a pinch of salt; cook 1 minute more. Set aside.
03 - Unroll crescent dough and separate into 8 triangles. Place a few slices of roast beef and sautéed onion mixture onto the wide end of each triangle. Sprinkle evenly with cheese.
04 - Roll up each triangle tightly from the wide end. Place seam-side down on the prepared baking sheet.
05 - Melt remaining butter and brush over tops of roll ups. Sprinkle with remaining black pepper and thyme if using.
06 - Bake for 12–15 minutes until golden brown.
07 - Combine beef broth and Worcestershire sauce in a small saucepan. Heat over low heat, simmering for 5 minutes to make the au jus sauce.
08 - Serve hot roll ups with warm au jus for dipping.