Mix together all the marinade ingredients in a non-metallic bowl, then add the lamb cutlets. Season to taste with salt and pepper, turn the cutlets to coat and set aside for 15 minutes to marinate.
Cook the cutlets under a preheated hot grill for 3–5 minutes on each side or until slightly charred and cooked through. Keep warm and allow to rest.
Meanwhile, cut the baked sweet potatoes into quarters, scoop out some of the flesh and brush the skins with oil. Season to taste with salt and pepper and cook for about 15 minutes under the grill until crisp. Serve with the lamb cutlets and rocket leaves.