How to Make It
Build a fire in a charcoal grill, or heat a gas grill to hot. Rub inside of lamb with 1 tablespoon olive oil, 1 tablespoon fennel seeds, 1 tablespoon rosemary, and next 4 ingredients. Roll lamb lengthwise into an evenly shaped piece, and secure by tying with string. Rub outside of lamb with remaining oil, fennel seeds, and rosemary.
Let grill cool to medium-high heat or 350° to 400°, and brown lamb over direct heat 5 to 7 minutes on each side. Push coals to 1 side of charcoal grill, or turn 1 side of gas grill off, and grill lamb over indirect heat 50 minutes to 1 hour or until internal temperature reads 145° for medium rare. Remove lamb from grill, cover loosely with aluminum foil, and let rest about 10 minutes before slicing. Serve warm or at room temperature with Mint Chimichurri.