Core and halve tomatoes. Slip some garlic into each half, then toss with olive oil, red pepper flakes, and oregano and season with salt and pepper. Brush rolls with olive oil. Grill rolls until toasted and tomatoes until tender. Season chicken and grill one side; flip, then top with Parmesan and mozzarella. Grill until chicken is cooked through and cheese is melted. Make sandwiches with rolls, chicken, and tomatoes.