Preheat oven to 400°F. Brush a sheet pan or 10-inch skillet with olive oil.
Stir together melted butter, minced garlic, Italian seasoning, salt, pepper, parsley, and red pepper flakes.
Separate biscuits. Gently flatten each to a 4–5 inch round without tearing.
Place one mozzarella cube and one meatball in the center of each round.
Pinch dough edges together to seal well. Roll seams under and set seam-side down on the pan.
Brush tops with about half of the garlic butter.
Bake 12–14 minutes until puffed and golden and the centers are hot.
Brush with remaining garlic butter. Sprinkle Parmesan over the tops and bake 2 more minutes.
Rest 5 minutes. Serve warm with marinara for dipping.