1Heat oven to 425°F. Lightly spray large cookie sheet with cooking spray.
2In 12-inch skillet, cook sausage over medium-high heat 8 minutes, stirring occasionally, until no longer pink. Push sausage to edges of skillet; add 1 tablespoon of the oil. Add onion and garlic; cook 5 minutes, stirring occasionally, until onion is softened. Remove from heat; stir in pizza sauce, oregano, pepper flakes and salt.
3With serrated knife, cut bread in half lengthwise; scoop out center of each bread half, leaving 1/2-inch border (discard removed bread or reserve for making bread crumbs). Place bread halves on cookie sheet. Spread 1/3 cup of the ricotta cheese down center of each; top evenly with sausage mixture, mozzarella cheese and Parmesan cheese. Drizzle loaves with remaining 1 tablespoon oil.
4Bake 6 minutes or until thoroughly heated and cheese is melted. Cut into slices. Sprinkle with chopped fresh parsley, if desired.