Preheat the oven to 200°C (fan)/220°C/gas mark 6.
Chop the potatoes (peel if wanted) into small pieces, place in a large roasting tin, drizzle with 2 tbsp sunflower oil and season with salt and pepper
Mix and put in the oven for 20 minutes. Stir halfway to stop them from sticking.
While the potatoes are roasting prepare your parsnips, carrots and Brussels sprouts. Peel the parsnips, cut out the core and cut into batons, peel the carrots and cut into batons and pull off any outer leaves from your Brussels sprouts and cut in half if on the large side.
Remove the potatoes from the oven and stir well.
Add the parsnips, carrots and sprouts, and the rosemary sprigs or sage leaves. Stir again.
Replace for 20 minute.
Remove from the oven, stir and then replace for a further 20 minutes.
If using add the frozen Quorn pieces, stir well and replace in the oven for 20 mins, stirring halfway.