01 - Preheat the oven to 400°F. Toss the diced squash with 1 tbsp olive oil, salt, and pepper. Spread on a baking sheet and roast for 20–25 minutes, turning once, until tender and golden. Set aside.
02 - Heat 2 tbsp butter and remaining 1 tbsp olive oil in a large sauté pan or Dutch oven over medium heat. Add sage leaves in a single layer and fry for 1–2 minutes until crisp. Remove with a slotted spoon and drain on paper towels.
03 - In the same pan, add onion and cook over medium heat for 4–5 minutes until soft and translucent. Add garlic and cook for 1 minute.
04 - Add Arborio rice and cook for 2 minutes, stirring constantly, until grains are glossy and coated.
05 - Pour in a ladleful of warm vegetable stock, stirring until absorbed. Continue adding stock one ladle at a time, stirring frequently and letting each addition absorb before adding the next, for about 18–20 minutes.
06 - When rice is creamy and al dente, fold in roasted squash. Stir in remaining 2 tbsp butter and grated Parmesan. Season with salt and pepper to taste.
07 - Plate immediately, topping with crispy sage leaves and extra Parmesan if desired.