In a small bowl, combine juice, jerk seasoning and oil. Rinse halved hens and pat dry with paper towels. Put the hens in a zip-top bag and pour in the marinade. Turn hens in the bag to coat evenly. Close the bag and refrigerate for 2 to 4 hours.
Preheat the oven to 400 degrees F.
Remove the hens from the marinade and place in a roasting pan, breast-side up. Pour the remaining marinade over the hens. Roast for 40 to 45 minutes or until cooked through and golden brown.
Garnish with cilantro.