Preheat the barbecue to medium heat. Trim a 1/2-inch off the top of each garlic bulb. Drizzle 1 Tbsp. of the oil on the exposed parts of the garlic, and then season with salt and pepper and set a rosemary sprig on top. Set the garlic on the upper rack of the barbecue, closed the lid, and cook 20 minutes, or until garlic cloves soften and begin to push out the top. Arrange garlic on a plate and cool to room temperature. While this occurs, brush the pita bread with remaining oil and quickly grill until nicely coloured on both sides. Cut pita into wedges and arrange it and the cheese alongside the garlic. Allow guests to spread the cheese and cloves of garlic on the grilled pita.