Preheat the oven to 400°F.
Toss squash, garlic, mushrooms and oregano in olive oil. Roast for 20 minutes. Keep warm.
Meanwhile, heat the chicken stock in a saucepan until it's simmering, then reduce heat to low.
In a separate large frying pan,melt the butter and sauté the onion until soft, but not browned. Add the rice and reduce the heat to low. Stir well to coat the grains of rice in the butter, for about 2 minutes.
Add the wine to the rice and turn the heat up to medium. Cook, stirring the rice continuously, until all the liquid has been absorbed (about 5 minutes). Add the warmed chicken stock slowly, stirring continuously so the rice cooks evenly. Continue stirring and cooking over medium heat until most of the liquid is absorbed, the rice is al dente and the risotto has a nice creamy texture. This will take around 20 minutes of cook/stir time. Remove from heat as soon as the rice is soft and completely cooked.
Stir in the roasted vegetable mixture and parmesan cheese.
Serve while still warm.