Preheat your oven to 400°F (200°C). Toss the butternut squash cubes with a drizzle of olive oil, salt, and pepper. Spread them on a baking sheet and roast for 20-25 minutes, or until tender and slightly caramelized.
While the squash is roasting, heat the olive oil in a large saucepan or Dutch oven over medium heat. Add the chopped onion and cook until softened, about 5 minutes. Stir in the minced garlic and cook for another minute until fragrant.
Add the Arborio rice to the pot and stir to coat with the oil. Cook for 1 minute, stirring constantly, until the rice is lightly toasted.
Pour in the white wine (or broth) and stir, scraping up any browned bits from the bottom of the pan. Cook until the liquid has mostly evaporated.
Add the hot vegetable broth, one cup at a time, stirring continuously until each addition is absorbed before adding the next.
Once all the broth has been added and the rice is cooked through but still has a slight bite (about 15-20 minutes total), stir in the roasted butternut squash and grated Parmesan cheese. Season generously with salt and pepper.
In a separate small skillet, heat a thin layer of olive oil over medium heat. Fry the sage leaves in the hot oil for about 30 seconds, or until crisp. Be careful, as the oil may splatter. Remove the sage leaves with a slotted spoon and drain on a paper towel.
Serve the risotto immediately, topped with the crispy fried sage leaves and extra grated Parmesan cheese.