Preheat oven to 475°F. Coat a large baking sheet with cooking spray.
Heat 1 tablespoon oil in a large nonstick skillet over medium-high heat. Add sausage and cook, breaking it into small pieces, until no longer pink, about 4 minutes. Add spinach and cook, stirring, until wilted, about 1 minute. Transfer the sausage and spinach to a large bowl; stir in mozzarella, ricotta, Italian seasoning, garlic powder and pepper.
On a lightly floured surface, roll dough into a 6-inch log and divide into 5 equal pieces. Pat and roll each piece into a 6-inch circle. Place 1/2 cup filling on one half of each circle, leaving a 1/2-inch border. Fold the dough over the filling and crimp the edges with a fork to seal. Cut several small slits in the top to vent steam; brush the calzones with the remaining 1 tablespoon oil. Transfer the calzones to the prepared baking sheet.
Bake the calzones in the lower third of the oven until browned on top, about 15 minutes. Let cool slightly before serving.