Preheat oven to 400°F (200°C). Toss the butternut squash with 1 tablespoon of olive oil, place on a baking sheet, and roast in the oven for 20 minutes or until tender.

In a large pan, heat 1 tablespoon of olive oil and 1 tablespoon of butter over medium heat. Add the chopped onion and garlic, cooking until the onion is translucent.

Add the Arborio rice to the pan and stir until the grains are well-coated and appear translucent with a white dot in the center, about 2 minutes.

Pour in the white wine and stir until it's mostly absorbed by the rice.

Add the saffron (including soaking water) and begin adding the warmed vegetable broth, one ladleful at a time, stirring continuously, allowing each ladleful to be absorbed before adding the next.

After about 18–20 minutes, when the rice is al dente and creamy, stir in the roasted butternut squash, remaining butter, and Parmesan cheese. Season with salt and pepper to taste.

Serve hot, garnished with additional Parmesan cheese if desired.