Preheat the oven to 400 degrees Fahrenheit.
Rinse the chicken and pat dry. Place it in a roasting pan.
Squeeze the juice from one of the grapefruits all over the chicken, both inside and out.
In a small bowl, combine the thyme, rosemary and paprika. Sprinkle the mixture all over the chicken, inside and out.
Stuff the cavity with the remaining two grapefruit halves.
Drizzle the chicken all over with the oil and salt.
Make a tent with foil, cover the chicken, and place in the oven. Bake for about 45 minutes, and remove the foil.
Roast for another 15 to 20 minutes, until the juices run clear, and the skin is browned.
Remove the chicken from the oven, and cover with foil again, allowing the meat to rest for about 10 minutes before carving.