Step 1: Strip enough rosemary leaves off the bunch to obtain 3 tablespoons finely chopped. Tie the remaining rosemary sprigs together at the stem end. Trim off any straggly leaves at the opposite end.
Step 2: Arrange the lamb chops in a single layer on a rimmed baking sheet (use 2 if needed). Generously season on both sides with the salt, pepper, garlic, rosemary, and hot pepper flakes. Drizzle olive oil over the chops and pat the flavorings into the meat with the flat part of a fork. Brush the lemon halves with olive oil and season with salt and pepper. Marinate the chops in the refrigerator for 20 minutes while you build your fire.
Step 3: Set up your grill for direct grilling and heat to high. In the best of all worlds, you’d grill over a wood fire. Barring that, add wood chunks or chips to your charcoal fire (or place wood chunks on the heat diffuser of your gas grill). Leave 1/3 of the grill fire-free as a safety zone.
Step 4: Fold two 12- by 18-inch pieces of aluminum foil lengthwise in thirds like a business letter. This is your grill shield—it will keep the exposed ends of the bones from burning.
Step 5: Brush and oil the grill grate. Arrange the lamb chops on grate in a neat row, rib bones facing the front. (Work in batches if needed.) Arrange the lemons cut sides down on the grate. Grill until the lamb chops and lemons are sizzling and browned on the bottom, 3 to 4 minutes. Transfer the lemons to a platter.
Step 6: Turn the chops and continue grilling until browned on both sides and cooked through, or to taste. (Italians like their scottadito medium to medium-well done.) At some point, the ends of the rib bones will start to burn: slide the foil grill shield under them. At some point, the dripping lamb fat may cause flare-ups. Move the meaty part of the chops onto the foil or away from the fire into the safety zone.
Step 7: Transfer the chops to a platter or plates. Squeeze lemon juice over them, garnish with cherry peppers, if desired, and eat—how else?—with your burning fingers.