Preheat oven to 350 degrees F. Grease a roasting pan or medium baking sheet.
Toss the squash with 2 tablespoons oil and season well with salt and pepper. Spread out on baking sheet and roast until tender about 1 hour.
Meanwhile in a large skillet heat the remaining tablespoon of oil and saute the onion and garlic seasoned with salt and pepper until tender.
If pan is dry add a touch more olive oil along with the rice. Toast the rice 2 - 3 minutes, stirring often. Add the rice and onion mixture to deep-sided, large casserole dish with a lid. Stir in the chicken broth and heavy cream.
Bake with the lid on about 40 - 45 minutes or until rice is tender. If there is still liquid left that is ok it will thicken as it stands.
Stir the butter and Parmesan into the rice then stir in the cooked squash. Garnish with parsley and serve.