Place the fillet skin side down on a sheet of foil. Season lightly with salt and pepper. Top the fish with fresh rosemary, sage leaves, lemon slices and pats of butter. Bring two edges of the foil together over the salmon and fold them together, leaving open space between the foil and the top of the fillet. Seal the ends of the foil pouch.
Preheat the grill to a medium-high temperature. Place the foil-wrapped salmon into the grill and close the cover. Cook the grilled lemon rosemary salmon for 3 minutes per half-pound, or until the flesh is opaque and can be flaked with a fork.
Check the thickest part of the fish for doneness, Taking it of the grill when the salmon looks a little undercooked in the center of the thickest part. The fish will continue cooking after it's removed from the grill, and will be perfectly done after resting for a few minutes.