If you’re cooking your veg separately, rather than with my perfect roast chicken, preheat the oven to 200°C/400°F/gas 6.Peel the vegetables, halving any larger ones lengthways. Break the garlic bulb into cloves, leaving them unpeeled, and bash them slightly with the palm of your hand. Pick the rosemary leaves.Put the potatoes and carrots into a large pan – you may need to use two – of boiling salted water on a high heat and bring back to the boil. Allow to boil for 5 minutes, then add the parsnips and cook for another 4 minutes.Drain in a colander and allow to steam dry. Take out the carrots and parsnips and put to one side.Fluff up the potatoes in the colander by shaking it around a little – it’s important to ‘chuff them up’ like this if you want them to have all those lovely crispy bits when they’re cooked.Put a large roasting tray over a medium heat and either add a few generous lugs of olive oil or carefully spoon a little of the fat from the meat you’re cooking, and add the garlic and rosemary.Tip the vegetables into the tray, season with a good pinch of sea salt and black pepper and turn the veg over to coat them in the flavours. Spread them out evenly into one layer – this is important, as you want them to roast, not steam as they will if you have them all on top of each other.Roast for 1 hour, or until golden and crisp, then serve immediately with your roast and some delicious gravy.