Preheat oven to 400 degrees. Place naan or pitas on a parchment-lined baking sheet; season with salt and pepper. Divide tomato sauce among naan and top with bocconcini or mozzarella, and meatballs. Bake until cheese is melted, about 10 minutes.
Toss arugula with lemon juice; season with salt and pepper. To serve, top pizzas with arugula, grated Parmesan, and red-pepper flakes.
You can crumble the meatballs or halve them.