Place an oven rack in the lower 1/3 of the oven. Preheat the oven to 450 degrees F.
Rinse the game hens and pat dry with paper towels. In a small bowl, mix together the olive oil, shallots, orange zest, lemon zest, thyme, mint, 1 teaspoon salt and 1 teaspoon pepper. Rub 2 tablespoons of the zest mixture over the skins of the game hens. Place the remainder of the zest mixture under the skin and into the cavities of the hens. Using kitchen twine, truss the legs together. Place the hens in a shallow 9 by 13-inch baking dish. Add the chicken stock, Marsala wine, lemon juice, orange juice, and cranberries. Roast for 30 to 35 minutes, or until the leg juices run clear. Remove the game hens and set aside. Place the flour in a small saucepan. Whisk in the pan juices. Bring the juices to a boil over medium heat. Reduce the heat and simmer for 8 to 10 minutes until slightly thickened. Whisk in the butter and season, to taste, with salt and pepper.
To serve, remove the kitchen twine and place the hens on 2 serving plates. Drizzle with the citrus-herb sauce.
Reserve 1/4 cup of the citrus-herb sauce for the Crouton Salad.