Preheat oven to 425°F. Toss butternut squash cubes with 2 tablespoons olive oil, salt, and pepper. Spread on a baking sheet and roast for 25-30 minutes until tender and caramelized, stirring halfway through.
Heat vegetable broth in a saucepan and keep at a gentle simmer. In a large, heavy-bottomed pot, heat remaining 1 tablespoon olive oil and 1 tablespoon butter over medium heat.
Add onion and cook until softened, about 4 minutes. Stir in garlic and cook 1 minute. Add rice and stir to coat with oil, toasting for 2 minutes until edges become translucent.
Pour in white wine and stir until completely absorbed. Begin adding warm broth one ladle at a time, stirring frequently and allowing each addition to be absorbed before adding more.
Continue adding broth and stirring for about 20-25 minutes until rice is creamy and tender but still has a slight bite. Stir in half of the roasted squash, mashing it slightly to incorporate.
Remove from heat and stir in remaining 2 tablespoons butter, sage, and Parmesan cheese. Season with salt and pepper. Top with remaining roasted squash cubes and serve immediately.