Preheat oven to 425 degrees F (220 degrees C). Nest 2 large aluminum turkey-roasting pans together for strength. Rinse and pat the turkey dry with paper towels, and place turkey into the doubled pans.
Place the sausage into a large skillet over medium heat, and cook until browned and crumbly, breaking it up into chunks as it cooks. Place the sausage with the pan drippings into a large mixing bowl.
Mix in the dry stuffing mix, green onion, parsley flakes, 1/2 cup of softened butter, sage, salt, and black pepper until thoroughly combined, then moisten the stuffing with the chicken broth. If stuffing seems dry, mix in water, about 1 tablespoon at a time, until stuffing is desired consistency.
Lightly stuff the main and neck cavities with the stuffing; place any extra stuffing into a baking dish, and cover with foil. Refrigerate the pan of stuffing. Generously rub the outside of the turkey with 1/4 cup of softened butter, or as needed; sprinkle the turkey with salt. Cover the turkey with foil.
Roast in the preheated oven until the turkey drumstick twists easily in the socket and the juices run clear, about 4 hours. Check the level of pan drippings, and remove excess drippings if needed. Roast turkey an additional 1 hour and recheck and remove drippings if necessary; bake an additional 30 minutes, and uncover the turkey.
Heat the oven's broiler. Broil the turkey, basting often, until golden brown, about 15 more minutes. An instant-read meat thermometer inserted into the thickest part of a thigh should read 180 degrees F (80 degrees C). About 2 hours before serving time, bake the pan of dressing if desired.
Stuffing should be wet like paste, not soupy. Add water only if necessary. Stuffing should still be able to be balled.