Heat the oven to 180°C (350°F). Lightly butter a baking dish that fits the rolls snugly.
Slice the whole slab of rolls in half horizontally with a long serrated knife. Put the bottom half in the baking dish.
Lay half the Havarti over the bottom rolls, then the sliced turkey in an even layer, then spoon over the cranberry sauce and spread it gently. Lay the rest of the Havarti on top. The cheese on both sides of the cranberry sauce melts and glues the filling together.
Place the top half of the rolls over the filling and press down gently.
Whisk the melted butter, Dijon, honey, poppy seeds, garlic powder, and rosemary in a small bowl. Brush it evenly over the tops of the rolls and let a little run down the sides.
Cover the dish tightly with foil and bake for 15 minutes. Take the foil off and bake for 5 minutes more, until the tops are golden and glossy and the cheese is melted.
Check the centre of the tray with a food thermometer — it should reach 74°C (165°F). Leave the sliders to rest for 5 minutes, then pull them apart and serve warm.