Give the pumpkin pieces a good stir and place the baking sheet in the oven. Roast them for 15 minutes or until they are lightly caramelized on the sides.
Add the white wine when the rice is hot enough and cook until all the alcohol evaporates. Turn the heat to low and start adding stock a ladle each time.
Add the butter and give it a vigorous stir. This stage is called mantecatura; the continuous stirring of butter into the risotto to develop creaminess.
Stir in the roasted butternut squash. Turn the heat off and add the grated Parmesan on top. Do not stir the Parmesan cheese in, and let the risotto rest for 5 minutes.