Best way to cook zucchini and carrots-- the link goes to a salsa recipe ??? But the best way to cook zucchini and carrots? Toss in olive oil, then sprinkle with salt and pepper. Roast at 450 for 25-30 minutes. (Or slow roast 275 for 3-4 hours). You can also sprinkle Parmesan cheese on it before roasting.