Preheat the oven to 350 degrees F. Lightly coat a rectangular baking dish large enough to hold your slider rolls with nonstick cooking spray.
Whisk together the melted butter, Worcestershire, Dijon, Italian seasoning, granulated garlic or garlic powder, and onion powder in a small bowl and set aside.
Without separating into individual rolls, slice the top half of the bread off the bottom and place the bottom portion of the rolls in the prepared baking dish. Layer the bread with the sliced Provolone, roast beef, and diced pepperoncini and then top with the other half of the rolls. Liberally brush the melted butter mixture over the tops of the rolls and sprinkle evenly with poppy seeds.
Bake, uncovered, for 12 to 15 minutes, or until the cheese has melted and the tops of the rolls are lightly toasted. Use a knife to slice the sliders and serve.
Cooking for a crowd? Use a larger baking dish and double the recipe!