In a medium bowl gently combine turkey, rosemary, fish sauce, sugar, and black pepper (try not to over mix the meat). Form into patties.
Heat grill or pan over medium high heat. Brush insides of buns and both sides of patties with oil (if grilling, brush grill grates as well). Cook each side for approx. 4 minutes or until cooked through *see Note 2 (time will depend on patty thickness and cooking heat).
Open buns and place inside face down on grill or pan and cook until lightly browned (usually cooks within a minute).