Remove the sausage casings, dice the onion, slice the carrots into thin rounds, dice the celery, and mince the garlic. Open the canned tomatoes and tomato sauce, measure the broth, chop the parsley, and grate the Parmesan.
Heat the olive oil in a Dutch oven over medium high heat. Add the sausage, break it into bite size crumbles, and cook 6 to 8 minutes until browned and no pink remains. Move the sausage to a paper towel lined plate and pour off extra fat, leaving about 1 tablespoon of drippings.
Reduce the heat to medium and add the onion, carrots, and celery. Cook 5 to 6 minutes until the onion is soft and translucent, scraping up the browned bits. Add the garlic and crushed red pepper flakes and cook 30 to 60 seconds until fragrant.
Pour in the chicken broth, diced tomatoes with their juices, and tomato sauce. Stir in the basil, oregano, salt, and black pepper, then return the sausage to the pot. Bring to a boil, reduce to medium low, and simmer covered for 20 minutes.
Raise the heat to medium so the soup bubbles gently. Add the refrigerated tortellini, stir well, and cook 5 to 8 minutes until tender and floating, stirring every minute or two.
Turn the heat down to low and stir in the baby spinach a handful at a time until wilted, about 1 to 2 minutes. Add the parsley, stir to combine, and taste for salt and pepper.
Ladle the hot soup into warm bowls, making sure each serving gets plenty of sausage and tortellini. Top each bowl with freshly grated Parmesan and extra red pepper flakes if desired, and serve right away.