Preheat the oven to 400°F (204°C) and line a baking sheet with parchment paper for easy clean-up.
Put the cubed squash evenly spaced on the baking sheet and drizzle with 2 tablespoon of the olive oil. Add salt and pepper to taste and toss to evenly coat. Roast for 15 minutes then shake and roast another 15 minutes, or until the squash in caramelized on the edges. Keep warm until the risotto is done.
In a risotto pan or a large heavy straight sided skillet, heat the remaining 2 tablespoon of olive oil and 3 tablespoon of vegan butter on medium heat until the butter is completely melted and beginning to bubble.
Add the leek to the pan and stir to coat. Cook for approximately 5 minutes or until it softens. Stir often.
Add the 1 ½ cups of arborio rice and stir to coat with the oil. Cook for two minutes to toast the rice, stir often.
Reduce the heat to low and add the 1 cup of wine or 1 cup of broth if you don't drink wine. Stir constantly until the wine is completely absorbed into the rice.
Add a 1 cup of vegetable broth and stir continuously (this prevents the rice from sticking to the pan) until the rice absorbs the broth. Continue adding a cup of broth, let the rice absorb it while stirring frequently, then add another cup of broth, until the rice is tender and creamy. Approximately 25 to 30 minutes.
Add the roasted squash, 1 tablespoon minced sage, 1 cup grated vegan parm, and salt and pepper to taste to the risotto and stir to combine.
Serve hot.