Preheat oven to 400 degrees. Place leg of lamb on a rack in a large roasting pan.
In a medium bowl, whisk together next 8 ingredients (garlic through almond meal) and 2 tablespoons of the olive oil.
Coat lamb with herb mixture, gently massaging into the meat on all sides. Roast, uncovered, for 30 minutes then reduce oven temperature to 350 degrees.
Place sweet potatoes, apples and onion in a medium bowl; drizzle with remaining 1 tablespoon of olive oil and salt and pepper to taste; toss to combine.
Arrange vegetables around the lamb in the roasting pan; continue to roast for 1 hour or until internal temperature of lamb reaches 130 degrees. Transfer roast to a cutting board and loosely tent with foil; allow it to rest for 15 minutes before slicing.