Pat-dry the chicken (including cavity) with paper towel.
Combine miso paste, soy sauce, vinegar, ginger and oil in a small bowl. Rub this miso mixture all over chicken, including the cavity.
Place chicken on a plate, then cover with foil and refrigerate for 1 hour to marinate, overnight if you can.
Preheat oven to 180°C. Take the chicken out of the fridge, and allow to come to room temperature. Place it in a roasting dish, breast-side up. Roast for 1 hour or until juices run clear from the when thickest part of the leg (pierce it with a skewer to check). Baste the chicken every 10 minutes or so with the pan juices.
Let it rest for 10 minutes (under cover) before carving.
Serve with the pan juices poured over the servings.