Preheat the oven to 400 degrees Fahrenheit. Place the cubed butternut squash on a baking sheet, drizzle with olive oil, and season with salt and pepper. Toss to coat. Put the tray in the oven, and bake for about 30 minutes, or until the squash is fork tender. When it is done cooking, remove from the oven and set aside.
Next, add 2 tablespoons of the unsalted butter and 1 tablespoon extra virgin olive oil to a large nonstick skillet. Warm over medium-low heat until the butter is melted. Add the onion and cook, stirring frequently, until the onions are tender and translucent but not at all browned. If they start to get any color, turn down the heat and continue cooking until softened. This should only take a few minutes.
Meanwhile, pour the chicken or vegetable stock into a small saucepan and bring to a simmer.
Once the onions are softened, add the arborio rice, sage, and garlic to the pan. Increase the heat to medium & sauté for a minute or two, until the garlic and sage are fragrant and the rice is coated with the butter and spices.
Add the white wine and cook until mostly evaporated. Next, add one ladle of warm stock to the pot and stir until the rice has absorbed most of it. Continue adding the stock, one or two ladles at a time,stirring until it has been absorbed by the rice before adding more. Continue until all the broth has been added and absorbed and the rice is tender but still has a little bite, about 25 minutes.
Turn off the heat, and stir in 1 additional tablespoon of butter, the parmesan cheese, and additional 1 tablespoon fresh minced sage. Stir to combine well, the gently fold in the roasted butternut squash. Season to taste with salt and pepper, and enjoy right away.