Place the Dutch oven over medium-high heat.
Add the sausage and brown, breaking up any large clumps.
Remove the sausage from the pot and drain on paper towels.
Return the Dutch oven to the heat and add the onions, carrots, rutabaga, fennel bulb, and garlic, sautéing until just becoming tender.
Add the chicken stock and bring to a simmer, cooking until the vegetables are fork tender.
Add the tortellini and return the soup to a simmer.
Remove the soup from the heat and transfer to bowls for serving.
Garnish with the parmesan cheese and parsley.