Preheat your oven to 400°F (200°C). Cut the spaghetti squash in half lengthwise and scoop out the seeds. Brush insides with olive oil and season with salt and black pepper. Place cut-side down on a baking sheet and roast for 35–40 minutes until fork-tender.

In a skillet over medium heat, cook the Italian sausage for about 5–7 minutes, breaking it apart with a spatula until browned. Stir occasionally.

Add minced garlic and sliced mushrooms to the skillet and cook for another 3–4 minutes until mushrooms soften.

Stir in fresh spinach and let it wilt for about 2 minutes. Then, add halved cherry tomatoes and sprinkle with Italian seasoning. Simmer for 2–3 minutes.

Remove roasted spaghetti squash from the oven and fluff strands with a fork. Spoon sausage and vegetable mixture evenly into each half.

Sprinkle shredded mozzarella cheese over the stuffed squash. Bake at 375°F (190°C) for 10–15 minutes until cheese is melted and golden.