Meanwhile, melt the butter in a large saucepan and add the onions. Fry for 2-3 mins until starting to soften, then add the vermicelli and cook until golden. Add the rice, saffron, stock and 500ml water. Cover with a lid. Bring to the boil, then reduce the heat and cook until the liquid has been absorbed, about 20 mins. Add the roasted carrots and parsnips, scatter the parsley over and serve.