Place the carrots, celery, onion, fennel bulb, chicken (you can use pre-cooked (shredded) or raw), chicken stock, tomatoes, basil, oregano, rosemary into a 6-quart slow cooker.
Cook on high for 3 hours or on low for 5 hours on high.
Taste and season with salt and pepper.
Place the tortellini and spinach into the soup and mix. Cook on high for another 15 minutes.