Heat the banana leaves over an open flame until pliable. Sprinkle the inside of the fish with salt and pepper, and stuff the cavity with the lemon, parsley, thyme, bay leaf, garlic, onion and red pepper. Coat the outside of the fish with olive oil and sprinkle with salt and pepper. Wrap the fish in the root beer leaves, then wrap in the banana leaves. Tie at intervals with butcher's twine to secure the leaves to the fish.
Bake until the fish reaches an internal temperature of 140 degrees F, 15 to 20 minutes, flipping once halfway through cooking.