Heat vegetable oil over medium heat in a large pot.
Add italian sausage to the pan and break it up into small pieces with a spatula.
Cook until fully browned, then remove from pan and set aside.
Add onion, celery, and carrot to the pot and season with salt and red pepper flakes.
Cook, stirring occasionally, until vegetables are softened ~5 minutes.
Mix garlic into the pot and cook for an additional minute.
Stir flour into the vegetables until they are well coated.
While stirring the vegetables continuously, slowly pour chicken stock into the pot.
Add rosemary, thyme, and bay leaf to the pot.
Bring the soup to a boil, then reduce to a simmer and cook for 10 minutes.
Mix in cream, then continue to simmer for 10 minutes.
Bring the soup up to a light boil, then add tortellini, italian sausage, and spinach to the pot.
Stir well, then continue to cook the soup for the length of time recommended on the package or tortellini. For our favorite brand it is 7 minutes.
Remove from heat and adjust salt and pepper to taste.