Preheat the oven to 230C/210C Fan/Gas 8 or its hottest setting.
Boil the potatoes in lightly salted boiling water for 3-4 minutes, then drain in a colander. Fluff up the edges using a fork, then season with salt and pepper, spray well with cooking oil spray.
Tip the potatoes into a large baking tray and roast for 25 minutes. Mix them around, spray with more cooking oil spray and roast for a further 25 minutes, until golden-brown all over.