Pre-heat oven to 425. Cover a sheet pan with foil and lightly spray the foil with non-stick cooking spray. Cut up the squash and put it in a bowl with the olive oil and toss to coat the cubes of squash. Place the squash on the foil and roast in the oven approximately 40-50 minutes or until tender. Add the nuts to toast just before the squash is done for a few minutes. Remove from oven when done and set aside.
For the Risotto:
Pour the stock into a 2-quart saucepan and keep it hot over low heat. (The liquid must be hot in order for the starch to be released to make the sauce creamy.)
Heat the olive oil in a wide 3 to 4 quart pan over medium heat then add in the chopped celery and onion, stirring occasionally until it is softened and translucent and just lightly golden.
Stir in the arborio rice and continue stirring until the grains are coated with oil and “toasted” – the edges become translucent – 1 to 2 minutes. Pour in the wine and let it boil, stirring the rice, until wine is evaporated.
Season the rice lightly with salt and ladle enough of the hot stock into the pan to barely cover the rice (1-2 ladles). Bring to a boil, then lower the heat so the stock is at a lively simmer. Cook until all the liquid has been absorbed and you can see the bottom of the pan when you stir – approx. 5-8 minutes.
Continue cooking the rice on simmer and pour add another 1/4 to 1/2 cup of the hot stock — each addition of the stock should be just enough to completely moisten the rice.
Continue the process of adding the stock and simmering until the rice is al dente. This total process should take approximately 15-20 minutes.
Taste the rice after the stock has absorbed to determine if the rice is seasoned and add salt and pepper to taste.
Add the roasted butternut squash and nuts to the risotto during the last 5-10 minutes of cooking.
Remove the pan from the heat and stir in the butter. Place into a serving platter and add the parsley and sage.