Preheat oven to 425 degrees F.
Line 2 baking pans with foil for easier cleaning. Set a baking rack in each pan. Split hens and butterfly open and place 3 hens in each baking pan. Season the hens with salt and pepper liberally. Mix the orange concentrate, balsamic vinegar and olive oil and pour evenly over the hens. Sprinkle with rosemary and roast 15 minutes at 425 degrees F and 30 minutes at 375 degrees F.