Preheat oven to 400F/200C
Combine crushed garlic, rosemary, lemon zest, salt and pepper and olive oil in a small bowl.
If your lamb is already wrapped, unroll the lamb and place on a clean board.
Spread half the rosemary marinade on the underside of the lamb.
Turn the lamb over and repeat the process on the outer side of the lamb.
Roll the lamb back together, and tie together with butcher's twine (see images in post).
Place lamb on a rack and place inside a deep baking tray.
Roast for 60-70 minutes for medium rare roast (or until it reaches around 145F).
Remove lamb, and cover with foil to rest for 15 minutes.
Use a sharp knife to carve off the lamb for serving.