Heat your oven to 180°C/350°FPeel and chop your root vegetables. Pop them into a large roasting tray.Pull the leaves off the rosemary stalks. Discard the stalks. Finely chop the rosemary. Scatter over the root vegetables. Salt generously.Melt your fat. Drizzle over the chopped vegetables and mix.Place in the oven for 30 minutes.While the root vegetables are cooking, wash the remaining vegetables. Chop the broccoli into small florets. Remove the base and outer leaves of the Brussles sprouts and chop in half. Remove the outer layer of the leek before wasning carefully to remove any dirt and slicing into coins. Wah and chop the zucchini.After 30 minutes, add the remaining vegetables to the roasting tray. Mix well. Roast for a further 30 minutes.