Preheat the oven to 220 c, 200 Fan, Gas Mark 7. Put the potatoes into a large shallow baking tray and add the chicken and sausages.
Arrange about 4 sprigs of rosemary among the chicken and sausages then finely chop the needles of another two sprigs so you have about 2 tsps of finely chopped rosemary. Sprinkle these over the chicken pieces.
Zest the lemon over everything and season with the salt and a good grinding of pepper. Drizzle with the oil then bake for 50-60 minutes until the chicken skin and the sausages are golden and the potato cooked through.
You can leave this to stand for up to 30 minutes before eating if you like.