01 - Preheat the oven to 400°F. Arrange cubed butternut squash on a baking sheet, drizzle with olive oil, season lightly with salt and pepper, and toss to coat. Roast for 25 minutes or until tender and lightly caramelized, stirring once halfway through cooking.
02 - In a large heavy-bottomed skillet, heat the remaining olive oil over medium heat. Add chopped onion and cook, stirring occasionally, until translucent, about 3 minutes. Add Arborio rice and stir constantly for 2 minutes to coat the grains evenly and lightly toast.
03 - Add a ladleful of warm vegetable broth to the rice, stirring gently and allowing the liquid to absorb. Continue adding broth, one ladleful at a time, stirring frequently and waiting for absorption before the next addition, until rice is creamy and al dente, about 20 minutes total.
04 - Reduce heat to low. Add roasted squash, grated Parmesan, butter, and chopped sage to the rice. Fold gently to combine. Taste and season with additional salt and freshly ground black pepper. Serve immediately, garnished with extra sage if desired.