Preheat the oven to 400°F (200°C).
Toss the diced butternut squash with olive oil, salt, and pepper in a bowl.
Spread the squash on a baking sheet in a single layer and roast for about 25-30 minutes, until tender and lightly browned.
While the squash is roasting, cook the macaroni according to package instructions until al dente, then drain.
In a large saucepan, heat the milk over medium heat until warm, then whisk in the garlic powder, nutmeg, and shredded cheese until smooth.
Once the cheese has melted and the sauce is smooth, stir in the roasted butternut squash and cooked macaroni.
Transfer the mixture to a greased baking dish and top it with bread crumbs.
Bake for 20-25 minutes or until the top is golden and bubbly.
Let it cool for a few minutes before serving to allow the sauce to set slightly.