Get Ready: Preheat your oven to 400°F (200°C).
Roast the Squash: Carefully slice the spaghetti squash in half lengthwise. Scoop out all the seeds. Lightly brush the cut sides with a touch of olive oil, then sprinkle with a pinch of salt and pepper. Place the squash halves cut-side down on a baking sheet. Roast for about 35 minutes, or until the flesh is tender enough to easily scrape with a fork.
Prepare the Sauce: While your spaghetti squash is roasting, gently warm up your prepared Keto Italian Meat Sauce. If you're using a store-bought low-carb marinara, for an extra hearty and healthy boost, consider browning some ground beef and Italian sausage to stir into it.
Shred the Squash: Once the roasted squash has cooled enough to handle, use a fork to gently scrape out the "spaghetti-like" strands into a large mixing bowl.
Combine Flavors: Pour about two-thirds of your delicious Italian meat sauce over the spaghetti squash strands. Gently mix everything together until all the squash is beautifully coated in the savory sauce.
Assemble the Casserole: Lightly spray a 9x13 inch casserole baking dish with nonstick spray. Pour the spaghetti squash and sauce mixture into the prepared dish, spreading it out evenly.
Top it Off: Spoon the remaining meat sauce evenly over the squash layer, then generously sprinkle with the shredded mozzarella cheese.
Bake to Golden Perfection: Place the casserole in the preheated oven and bake for 15-20 minutes, or until the cheese is melted, bubbly, and a lovely golden brown.
Serve and Enjoy: Let it cool for a few minutes before serving.