- Preheat your oven to 350°F (175°C). 
- Without separating the rolls, slice the entire pack in half horizontally. Place the bottom half in a baking dish. 
- Layer roast beef evenly over the rolls, followed by the cheddar cheese. 
- Place the top half of the rolls over the cheese to form sandwiches. 
- In a small bowl, whisk together melted butter, Dijon mustard, Worcestershire sauce, minced onion, garlic powder, salt, and pepper. 
- Brush the mixture generously over the tops of the rolls. 
- Cover the dish with foil and bake for 15 minutes. 
- Uncover and bake an additional 5–7 minutes, until the tops are golden and the cheese is melted. 
- Sprinkle with chopped parsley if desired, then slice and serve warm.