Mix the bread crumbs, parsley, mint, rosemary, 1/2 teaspoon salt, and 1/2 teaspoon pepper together in a small bowl. Drizzle with olive oil and stir to combine. Set aside.
Bring lamb to room temperature. Light one chimney full of charcoal. When all the charcoal is lit and covered with gray ash, pour out and arrange the coals on one side of the charcoal grate (modified two-level). Set cooking grate in place, cover gill and allow to preheat for 5 minutes. Clean and oil the grilling grate. Season the racks liberally with salt and pepper. Place the lamb fat side down close to, but not directly over, the coals. Cover and grill until well browned, about 8 minutes, turning 180 degrees half way through. Remove racks from the grill and place fat side up on a platter or cutting board.
Spread the mustard over the fat side of the lamb. Carefully press the breadcrumb mixture into the mustard on each rack.
Place the racks back on the grill, fat side up, close to, but not directly over, the coals. Continue to cook until an instant read thermometer registers 130F when inserted into the side of the rack, another 8 to 10 minutes. Remove from the grill and let rest uncovered for 10 minutes. Cut between each rib into chops and serve.