Heat oven to 375 degrees. Rinse and pat dry the game hens.
Mix the cocoa, five spice powder, salt and black pepper in a small bowl. Place the hens in a shallow dish, and sift the rub mixture over them, rubbing into their skins all over.
Heat the olive oil in a wide, oven-proof skillet (cast iron is good) over a medium flame. When the oil is hot, place the birds breast side down in the pan setting aside the dish the the birds were in and any leftover rub. Sear the breast for 3 to 4 minutes and then loosen them with a spatula taking care not to tear the delicate skin and then flip.
Add the shallots to the pan and saute’ for another 4 or 5 minutes.
While birds and shallots cook, mix the balsamic vinegar, honey and water in the shallow dish the birds were in. Scrape any leftover spice rub into the liquid. When the shallots are lightly browned and blistered, add the vinegar/honey/rub mixture to the skillet, add the grapes and rosemary sprigs and then shake the pan to loosen the birds and deglaze the pan.
Immediately put the skillet in the hot oen and roast for 45 minutes to 1 hour or until the internal temperature of the thickest part reads 165 degrees. Remove the skillet from the oven.
Arrange the roasted birds and the grapes on on a platter. While they rest, place the skillet over a medium-high flame and reduce the drippings and the shallots to a jammy glaze. This will take about 5 minutes. Pour the glaze over the birds or serve it in a gravy dish, tableside.