Heat the olive oil in a large pot over medium-high heat. Add the sausage and cook for approximately 4-5 minutes until browned, stirring frequently and breaking up large pieces with a wooden spoon or spatula.
Drain excess oil from the pot, if desired.
Lower the heat to medium and add the onions, carrots and celery to the pot. Cook for 3 minutes, stirring frequently.
Add the garlic, oregano, basil, thyme, black pepper and crushed red pepper (if using). Stir well and cook for 1 minute.
Add the diced tomatoes, chicken broth and water to the pot. Stir well, gently scraping any bits off the bottom. Raise the heat to high and bring the broth to a boil.
When the liquid is boiling, lower heat to medium-low and cover the pot. Cook the soup, keeping it at a simmer for 15 minutes, stirring occasionally.
Add the tortellini to the soup and stir. Raise the heat to medium to get the broth boiling. Cook the tortellini, uncovered for 6-8 minutes. Follow the cooking time recommended on the package. Keep the liquid boiling gently; raise or lower the heat as needed.
Add the greens to the soup and cook for 2-3 minutes until they’re wilted, stir occasionally.
Taste the soup and add salt if needed. As a reference we added ¼ teaspoon to ours.