HEAT oil in large skillet over medium-high heat. Add onion; cook for 2 minutes. Add sausage, garlic, oregano and red pepper flakes; cook for 3 minutes, stirring to break sausage into pieces. Season with salt and pepper, if desired.
TRANSFER mixture to slow cooker along with sauce, tomatoes, water and wine; stir. Cover; cook on low setting for 7 to 8 hours or on high setting for 3 to 4 hours.
STIR in pasta and spinach; top with cheese. Cover; cook on low for 15 minutes or until tender.
Cook’s Tip: Can use 1 package (20 ounces) or 2 packages (9 ounces each) of any filled pasta.