Allow rolls to thaw enough that you can cut through them. Remove rolls from pan. Do not separate.
Slice through the whole group of rolls from the side, creating the top and bottom of a sandwich.
Spread bottom half with 2 tablespoons pesto. Top with tomato slices. Sprinkle with salt & pepper. Top with mozzarella cheese slices. Spread 2 tablespoons of pesto over cheese slices. Turn top half of rolls over so sliced side is facing up. Place on top of sandwich. Press down slightly to flatten.
Cook in a panini grill until done. (Alternate cooking method: heat a skillet, sprayed with non-stick cooking spray, over medium low heat. Place panini in skillet. Place smaller skillet on top of sandwich and press down to flatten. Cook 1-2 minutes on each side.)