Preheat the oven to 200C/400F/Gas 6.
Combine the sage and rosemary with the salt and freshly ground black pepper.
Cut small incisions all over the chicken and stuff the herb mixture into these.
Place the potatoes and garlic in a roasting tray. Drizzle with olive oil and place the chicken on top. Generously season with salt and freshly ground black pepper, then roast for about one hour or until the juices run clear and the potatoes are lightly browned.
Once cooked cut the chicken into individual portions for 4-5 people. Arrange the chicken portions on top of the potatoes and return to the oven for another five minutes.
Allow the chicken to rest for 10 minutes before serving.