Preheat the oven to 200°C (180 fan) | 400°F | gas 6.
Spread out the peppers in a roasting tin, drizzle with oil and season with salt and pepper.
Roast in the oven for at least 40 minutes or until blackened in places and starting to collapse.
To remove the skins, immediately transfer the peppers to a heatproof bowl and cover with clingfilm. Leave to steam for at least 10 minutes or until they're cool enough to handle, then peel away the skins and remove the stalks and seeds.