IMPORTANT Because bunches of rainbow carrots are not all same sizes, most of the regular sized ones will be ready after 35 minutes. If you have any larger sizes, they may take an extra 10-15 minutes. Take the carrots which are cooked out and set them on a plate until the others continue to roast. The best way to test if they are cooked is by piercing them with the tip of a sharp knife. It should go into the carrot with little resistance.