To make the rub, mix all of the ingredients together in a bowl.
To make the butter, mix the butter and tarragon together in a small bowl.
To make the chicken, preheat the oven to 220C/200C Fan/Gas 7.
Spread the rub all over the chicken. Push the tarragon butter under the chicken skin.
Place all of the roast ingredients, except the chicken, in a large roasting tin. Drizzle with some oil and season with salt and pepper.
Place the chicken, skin-side down, directly on the bars of the oven with the roasting tin underneath. Roast for 1 hour, tossing the vegetables occasionally.
Check that the chicken is cooked through when the juices run clear with no trace of pink when the thickest part of the leg, between the drumstick and the thigh, is pierced with a skewer.
Once the chicken has rested for 10 minutes, joint the chicken and serve with vegetables and all the chicken juices from the tray.
