Preheat the oven to 350°F and lightly grease a 9×13 pan.
Heat the marinara in a pot on the stove top. Add the meatballs and heat until warmed through.
Cut the rolls in half and place the bottom buns in the prepared pan. Place 3 meatballs on each bottom bun. Top with additional sauce, a slice of mozzarella, and a few pieces of basil. Place the top buns on each slider.
In a bowl, mix together the melted butter, garlic, garlic powder, and parsley. Brush the mixture evenly over the tops of all the buns. Sprinkle on the parmesan cheese.
Cover with foil and bake for 20 minutes. Remove the foil and continue baking for another 5 minutes.