Preheat oven to 350 degrees F.
Using small fish tweezers remove pin bones from the length of the salmon and discard.
Place salmon skin side down on tin foil in a large roasting pan and season with a tablespoon of butter, salt and pepper. Place the sprigs of rosemary and lemon slices over the salmon so that they are overlapping and form a tent over the salmon. Wrap each salmon in the tin foil and roast for 15 minutes or until internal temperature reaches 145 degrees F on an instant-read thermometer.
Remove the salmon from the oven and bring to a well ventilated outdoor area. Light the oven dried rosemary on fire over the salmon. Let the ash fall over the salmon leaving streaks of concentrated rosemary flavor.
Using a large fish spatula, remove the side of salmon from the roasting pan and place on a platter. Garnish with sprigs of fresh rosemary and lemon wedges.