Heat olive oil in a large stockpot over medium heat. Add diced carrots, celery, onions, and garlic, and sweat for 2-3 minutes until softened.
Sprinkle oregano, salt, and pepper, and flour; stir vegetables until flour blends in. Add Italian sausage and break apart with a wooden spoon. Sauté until just cooked, about 4-5 minutes.
Add chicken broth, water, and tomato paste. Stir and heat for 1-2 minutes until tomato paste is fully blended with other liquids.
Stir in tortellini and beans. Heat soup over medium-high until tortellini is cooked: for frozen tortellini, about 7-8 minutes; for fresh tortellini, about 5-6 minutes.
Serve immediately and garnish with chopped parsley.
Notes
Best served immediately, but this sausage tortellini soup will keep in the refrigerator for up to three days. You can also freeze this soup in an airtight freezer-friendly container for up to 3 months.