Brown the Italian sausage in a skillet over medium heat, breaking it into crumbles. Drain any excess grease.
Transfer the cooked sausage to the crockpot.
Add the onion, garlic, chicken broth, diced tomatoes, tomato sauce, Italian seasoning, paprika, salt, and black pepper.
Cover and cook on Low for 5 to 6 hours or High for 2½ to 3 hours.
About 30 minutes before serving, stir in the tortellini and chopped spinach.
Add the heavy cream and Parmesan cheese, stirring until well combined.
Cover and cook for another 20 to 30 minutes, or until the tortellini is tender.
Garnish with fresh basil or parsley and serve warm.