Preheat oven to 350 degrees F. Cut squash in half lengthwise. Seed and peel squash; cut into 1-inch pieces (you should have about 2 2/3 cups).
Place squash in an 8x8x2-inch or 9x9x2-inch baking pan. Drizzle with oil and sprinkle with salt and pepper; toss gently to coat. Roast, uncovered, about 30 minutes or until tender, stirring once.
Transfer squash to a medium bowl. Mash with a fork or potato masher. Stir in cheese and nutmeg.
In a large mixing bowl, add all of the ingredients, and mix until the ingredients come together to form a dough. Turn the dough out onto a floured surface, and knead until smooth and elastic, about 10 to 15 minutes. Wrap in plastic wrap and set aside.
Preheat the oven to 350 degree F.
Combine the beef, veal, onion, celery, carrots, salt, and pepper in a roasting pan and roast until cooked through, about 1 hour. Let cool.
Add the spinach, then grind ingredients in a meat grinder with a fine grind. Add the eggs and cheese, and mix well to create a paste-like texture.
Roll out the dough on a floured surface using a rolling pin. Make a large, very thin layer of dough. Spread out a thin layer of filling on half of one side of the dough, using a spatula. Fold the dough end over the filling side of the dough. Mark the filled dough with a ravioli marker (ravioli rolling pin). Cut ravioli out using a ravioli cutter. Freeze until hard.
Make an egg wash by mixing together the eggs and milk. Add the ravioli to the wash, then dip in the seasoned bread crumbs. Refreeze until ready to fry.
Preheat a deep fryer to 350 degree F.
Fry the ravioli until golden brown. Serve hot on a plate sprinkled with freshly grated Parmesan on top and tomato sauce on the side.