2) 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 mins at 220C/Gas 7, then reduce heat and roast 30 mins at 190C/Gas 5.