Cut the spaghetti squash in half lengthwise and remove the seeds.
Brush each half with olive oil, salt, and pepper, then place the squash, flesh side down, on a baking sheet. Bake at 400°F (200°C) for approximately 45 minutes.
In a hot pan, add olive oil and sauté the onions, carrots, celery, garlic, yellow bell pepper, and banana pepper. Season and let cook slightly.
Remove the casing from the sausages and crumble the meat into the pan. Once the meat is well cooked, add the marinara sauce.
Incorporate a pinch of crushed red pepper, parsley, and parmesan into the sauce. Let it simmer while preparing the squash.
Shred the inside of the squash with a fork. Add some of the sauce to the squash and mix to evenly distribute it to the bottom.
Top the squash with a bit more sauce, parmesan, and parsley.