Preheat oven to 450°F. Line large rimmed baking sheet with foil. Combine 6 teaspoons salt and 2 teaspoons pepper in small bowl. Sprinkle inside of hens with half of salt and pepper mixture. Place 2 garlic cloves and 3 sage leaves inside each.

Using fingertips, loosen skin of game hen. Place 1 sage leaf under skin of each breast. Sprinkle outside of each hen with remaining salt and pepper mixture. Rub hens with oil and minced sage. Place hens, breast side up, on prepared baking sheet.

Roast hens 10 minutes. Reduce heat to 425°F; continue baking until juices run clear when hens are pierced with small knife, and meat thermometer inserted into thigh registers 180°F, about 30 minutes.