Preheat the oven to 200°C, fan 180°C, gas 6. Put the duck legs and shallots in a large roasting tin. Pour half the orange juice around the duck then roast for 1 hour.
Meanwhile, bring a large pan of water to the boil and add the potatoes and parsnips. Boil for 4-5 minutes, then drain well and set aside.
Once the duck has had 20 minutes in the oven, add the potatoes and parsnips to the roasting tin, turning to coat in the pan juices. Season with black pepper then return to the oven for the remaining 40 minutes, turning the vegetables once.
Make the marmalade glaze: put the marmalade, vinegar and remaining orange juice in a small pan and heat gently until the marmalade has melted. Bring to the boil, then simmer for 20 minutes until reduced by about half.
Drizzle 4 tablespoons of the marmalade glaze over the duck and roast for a further 15-20 minutes until the duck skin is crisp and golden, and the vegetables are golden and tender.
Just before the end of the cooking time, cook the beans in a pan of boiling water for 5 minutes, or until just tender. Drain and serve with the duck, vegetables with the remaining marmalade glaze.