Preheat your oven to 400°F (200°C). On a large baking sheet, toss the cubed butternut squash with 1 tablespoon of olive oil and a pinch of salt. Roast for 20 to 25 minutes until the squash is tender and the edges are lightly caramelized.
While the squash is roasting, pour the vegetable broth into a medium saucepan and bring to a low simmer over medium-low heat. Keep the broth warm throughout the entire cooking process.
In a large heavy-bottomed pot or Dutch oven, heat the remaining 1 tablespoon of olive oil and the butter over medium heat until the butter is melted and foamy.
Add the diced onion to the pot and sauté for 5 to 6 minutes, stirring occasionally, until translucent and soft. Add the minced garlic and cook for 1 minute more until fragrant.
Add the Arborio rice to the pot. Stir constantly for 2 to 3 minutes to toast the grains. The rice is ready when the edges of the grains look translucent while the center remains opaque.
Stir in the apple cider vinegar to deglaze the pan, scraping up any browned bits from the bottom. Continue stirring until the liquid has been fully absorbed by the rice.
Add one ladleful (about 1/2 cup) of the warm vegetable broth to the rice. Stir frequently and gently. Wait until the broth is almost completely absorbed before adding the next ladleful.
Continue adding broth one ladle at a time, stirring frequently. This process should take about 20 to 25 minutes. The risotto is finished when the rice is creamy and tender but still has a slight firm bite (al dente). You may not need all 6 cups of broth.
Once the rice reaches the desired consistency, remove the pot from the heat. Gently fold in the roasted butternut squash, grated Parmesan cheese, and chopped fresh sage.
Season the risotto with salt and ground black pepper to taste. Serve immediately in warm bowls, garnished with extra Parmesan or sage if desired.