Preheat the oven to 350°F (175°C). Grease a baking dish or line it with foil for easier cleanup.

In a skillet over medium heat, warm the olive oil and 2 tablespoons butter. Add the sliced onion and cook for 6 to 8 minutes, stirring occasionally, until softened and lightly caramelized.

Stir in the Worcestershire sauce, garlic powder, onion powder, Dijon mustard, dried thyme, salt, and black pepper. Add the beef broth and bring the mixture to a gentle simmer. Reduce heat and keep warm.

Slice the slider rolls in half horizontally, keeping the top and bottom halves connected if possible. Place the bottom halves in the prepared baking dish.

Layer the roast beef evenly over the bottom rolls, then spoon some of the cooked onions over the beef. Top with the provolone cheese slices, then place the top halves of the rolls over the cheese.

Brush the tops of the rolls with melted butter and sprinkle with sesame seeds if using.

Cover the dish with foil and bake for 10 minutes. Remove the foil and bake for 5 to 8 minutes more, until the cheese is melted and the tops are lightly golden.

Cut into individual sliders and serve warm with the reserved beef broth mixture for dipping.