Heat the oven to 425°F and line a baking sheet with parchment. Mix turkey, egg, breadcrumbs, ricotta, Parmesan, salt, oregano and garlic powder just until combined.
Shape into 12 equal meatballs with slightly flattened bases. Bake for 16 to 20 minutes until each reaches 165°F.
Lower the oven to 350°F. Split the connected Hawaiian rolls horizontally and place the bottoms in a parchment-lined 9-by-13-inch pan.
Lay half the provolone over the bread, place one meatball over each roll and spoon marinara evenly over them. Add remaining provolone and the top slab.
Brush with melted butter, cover with foil and bake for 15 minutes. Uncover for 8 to 10 minutes until the center reaches 165°F.
Rest for 5 minutes and cut along the roll seams into 12 sliders.