Preheat the oven to 350°F (175°C) with a rack in the middle. In a small bowl, combine the melted butter, 1 Tbsp Dijon, Worcestershire sauce, poppy seeds, garlic powder, and salt.
Slice the connected rolls horizontally into top and bottom slabs. Spread the separate 2 Tbsp Dijon evenly over both cut surfaces.
Put the bottom slab in a 9-inch square metal pan. Layer half the Swiss cheese, all the ham, and the remaining Swiss cheese over it. Replace the roll tops and spoon the butter sauce evenly over them.
Bake uncovered for 22–25 minutes, until the tops are golden and toasted, the cheese is melted through the center, and the middle rolls feel warm.
Cool in the pan for 15–20 minutes. Transfer the complete slab to a cutting board and divide it into 12 sliders.