Soak the rosemary sprigs in water for at least 1 hour prior to grilling the souvlakia.
Trim the leg of lamb of any excess fat and cut into 1 1/2 inch cubes. Place the cubes in a mixing bowl. Add the garlic, chopped rosemary, olive oil and salt and toss to coat. Refrigerate for at least 1 hour and up to 12 hours.
Remove the lamb from the refrigerator and skewer 4 pieces onto each rosemary sprig.
Heat a grill top for 5 minutes. Place the souvlaki on the grill and cook 1 1/2 to 2 minutes per side. Keep warm in a low oven until all are finished, transfer to a decorative platter and serve with lemon wedges.