Heat the oven to 400°F. Toss the cubed squash with 1 tablespoon olive oil, salt, and pepper. Spread on a baking sheet and roast for 25 minutes until tender and lightly browned.
Warm the vegetable broth in a saucepan over low heat.
In a large pot, heat 1 tablespoon olive oil and the butter over medium heat. Add the onion and cook until soft. Stir in the garlic for one minute.
Add the Arborio rice and stir for two minutes until the grains look slightly toasted.
Ladle in one cup of warm broth and stir until mostly absorbed. Continue adding broth one cup at a time, stirring often, until the rice is creamy and tender. This takes about 20 minutes.
Stir the roasted squash and Parmesan into the finished risotto. Taste and add more salt if needed.
In a small skillet, heat the remaining tablespoon of olive oil over medium heat. Fry the sage leaves for 30 to 45 seconds until crisp. Drain on a paper towel.
Spoon the risotto into a serving dish and scatter the crispy sage on top.