Preheat grill to medium heat, 350 to 400 degrees. Grease grill grates or grill basket with non-stick spray or brush with olive oil. Grill peaches skin up for 2 to 3 minutes or until slightly tender and grill marks form. Remove from grill. Let peaches cool slightly, slice into wedges; place cheese on one side and wrap with prosciutto. Garnish with rosemary and lightly drizzle with balsamic vinegar, if desired.