Preheat oven to 400°F. Butter 13x9-inch baking dish and set aside.
Place butternut squash on a baking sheet in a single layer. Drizzle with oil and season with salt and pepper; toss to coat. Roast 20 minutes, stirring occasionally, until tender. Transfer to a large bowl to cool.
Meanwhile, melt butter in heavy bottom large skillet over medium heat. Add leeks, celery, and fennel and cook 8 minutes. Add sausage and cook 10 minutes, or until vegetables are tender and sausage is cooked through, breaking up sausage while cooking. Add parsley, sage and marjoram. Stir and cook 1 minute. Add sausage and vegetables to bowl with butternut squash.
Reduce oven temperature to 350°F.
Divide bread between 2 rimmed baking sheets. Bake until bread is crusty but not hard, reversing sheets after 5 minutes, 10 to 12 minutes total. Add to bowl with butternut squash.
In a separate bowl, whisk chicken stock, eggs, Parmesan cheese, salt and pepper. Pour 1 cup of liquid over bread and vegetables tossing to combine evenly and adding more liquid in ¼-cup increments as needed if dry. Transfer stuffing to prepared dish.
Bake, uncovered, about 60 minutes, or until cooked through and brown and crusty on top. Remove from oven and let cool 10 minutes.