Heat the oven to 350°F and lightly grease a 9-by-13-inch baking dish. Keep the Hawaiian rolls connected, and slice the entire package horizontally to create one top section and one bottom section.

Place the bottom half of the connected rolls in the prepared baking dish. Layer the thinly sliced roast beef evenly over the bread, gently folding any large slices so the filling reaches from edge to edge.

Arrange the provolone slices over the roast beef, using 8–12 slices or about 8 ounces. Set the top half of the rolls over the cheese and press gently so the sandwich stack sits evenly.

Whisk the melted butter, Worcestershire sauce, Dijon mustard, garlic powder, onion powder, poppy seeds, and optional dried minced onion in a small bowl. Continue whisking until the mustard is dispersed and the mixture looks evenly seasoned.

Pour or brush the butter mixture evenly over the tops of the rolls, allowing some of it to run down the sides. Cover the baking dish tightly with aluminum foil so the bread stays soft while the cheese melts.

Bake the covered sliders for 15–20 minutes, until the cheese is melted and the roast beef is hot. Remove the foil and continue baking for 3–5 minutes, until the tops are lightly browned.

Let the sliders rest briefly, then cut along the connected rolls to separate them into 12 individual sandwiches. Serve warm while the provolone is soft and melty.