Preheat your oven to 400°F (200°C).

Prepare the hens: Remove the giblets from the cavities of the Cornish game hens. Pat the hens completely dry inside and out with paper towels. This is crucial for achieving crispy skin.

Season the hens: In a small bowl, combine olive oil, salt, pepper, dried thyme, dried rosemary, and garlic powder. Rub this mixture all over the outside of both hens.

Stuff the cavities: Place half a lemon, a sprig of fresh rosemary, and a sprig of fresh thyme inside the cavity of each hen.

Truss the hens (optional but recommended for even cooking): Tie the legs together with kitchen twine and tuck the wing tips under the body. This helps the hens maintain a neat shape and cook more evenly.

Roast the hens: Place the prepared hens in a roasting pan, breast-side up. If using butter, brush the melted butter over the hens for an extra crispy skin.

Roast for approximately 45-55 minutes, or until the internal temperature reaches 165°F (74°C) in the thickest part of the thigh, avoiding the bone. The juices should run clear when pierced.

Rest the hens: Once cooked, carefully remove the hens from the oven and let them rest for 5-10 minutes before carving. This allows the juices to redistribute, resulting in a more tender and moist bird.