Peel the carrots. Cut each one into halves widthways, then each piece in half lengthways. If your carrots are very thick, you may like to cut each piece lengthwise again. Place the carrot pieces in a roasting dish and pour over the oil.
Peel and grate the root ginger and add to the carrots with the orange zest. Mix everything together well so that the carrots are coated in the oil, ginger and zest.
Roast in the preheated oven for 40-50 minutes, until the carrots are soft and starting to brown. Serve immediately.