In a large skillet brown the sausage an onions for 6-7 minutes, breaking up until it is cooked through and the onions are soft. Add in the garlic and cook for 1 minute, until you can just start to smell it.
Add the browned meat to your crock pot along with the the crushed tomatoes, chicken broth, basil, oregano, Italian seasoning, red pepper flakes, salt and pepper. Cover and let simmer for 2-3 hours on high or 4-5 on low.
About 30 minutes before you are ready to serve, stir in the spinach, heavy cream, and tortellini.
Once the pasta is cooked taste and adjust seasoning.
Serve with fresh basil or Parmesan cheese if desired.