01 - Preheat oven to 400°F. Toss the diced squash with 1 tablespoon olive oil, salt, and pepper. Spread on a baking sheet and roast 20 to 25 minutes, turning halfway, until tender and caramelized.
02 - Heat remaining 1 tablespoon olive oil and 1 tablespoon butter over medium heat in a large saucepan. Cook onion until softened, about 3 minutes. Stir in garlic and cook for 1 minute.
03 - Add Arborio rice and cook, stirring, until grains are glossy and lightly toasted, approximately 2 minutes.
04 - Pour in white wine and stir until almost fully absorbed.
05 - Add warm vegetable stock one ladle at a time, stirring frequently, allowing each addition to absorb before adding the next. Continue for 18 to 20 minutes until rice is creamy and al dente.
06 - Stir in roasted butternut squash and chopped sage; cook 2 minutes until heated through.
07 - Remove from heat and stir in remaining 2 tablespoons butter and grated Parmesan. Adjust salt and pepper to taste.
08 - Serve immediately, optionally garnished with extra sage leaves and Parmesan cheese.