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