Preheat oven to 400 degrees.
Cut ends off acorn squash, cut in half and remove seeds.
Drizzle squash with olive oil, add salt & pepper to taste.
Place squash, cut side down, in bottom of a pan with a little water and bake 20 minutes.
In pan heat olive oil on medium heat. Add: onion, celery, salt & pepper, & rosemary. Sauté until onions are clear.
Add garlic and sausage. Cook till sausage is browned.
Add apple and cook till soft.
Mix in bread crumbs & parmesan cheese. Remove from heat.
Once squash is baked, fill with stuffing. Put back in the oven for about 20 minutes. Near the end of the cook time sprinkle more parmesan cheese.