Preheat the oven to 200°C / fan 180°C / gas 6. Put the potatoes in a large roasting tray, drizzle all over with the oil and add the rosemary. Season with black pepper and toss to combine.
Roast for 45 minutes, tossing halfway through, until tender and golden.
To serve, transfer to a serving dish and scatter over the chives and parsley.