Preheat the oven to 220ºC, fan 200ºC, gas 7. Wash and trim the carrots (halve any larger ones). Parboil for 5 minutes and drain.
Place in a large roasting tin with the frozen British roasting parsnips and the olive oil. Toss to coat. Roast for 30 minutes, stirring occasionally, until golden.
Drizzle over the maple syrup and roast for a further 10 minutes. Transfer to a warmed dish and serve sprinkled with parsley, if you like.