If you don't have a cooling rack, you'll probably want to stir the veggies a couple of times during cooking. Toss the still-frozen veggies with olive oil, and season generously with salt and pepper. Spread the veggies on the cooling rack, and roast for 10 minutes. Boost the oven temperature to 450Â°F, and roast veggies for another 30 minutes, or until they are nice and browned around the edges.