1. Preheat oven to 425ºF. Mist a baking sheet with nonstick cooking spray. Combine ricotta, mozzarella and spinach in a bowl.
2. Divide dough into four equal pieces and roll each piece into an 8-inch circle. Spoon 2 Tbsp. sauce in center of each dough round and spread over dough, leaving a 1-inch border. Divide cheese mixture among dough rounds and spread over tomato sauce. Top each dough round with meatball halves.
3. Fold dough over filling to create half-moon shapes. Press edges to seal. Bake until golden, 18 to 22 minutes. Serve with remaining sauce for dipping.