In a skillet over medium heat, cook the Italian sausage until browned. Drain any excess fat and transfer the sausage to the crockpot.
Add the garlic, diced tomatoes, tomato sauce, chicken broth, basil, oregano, and salt. Stir everything together.
Cover and cook on low for 4-5 hours or on high for 2-3 hours.
About 30 minutes before serving, stir in the heavy cream. Then add the cheese tortellini and spinach. Cover and cook about another 20-30 minutes until the tortellini is cooked.