Marinate your lamb in the wine, mustard, garlic and olive oil for at least 1 hour.
Chop sweet potato into 2 cm cubes, place into a baking tray and roast at 200c for 30 minutes, then add zucchinis, carrots and onion which have been cut to the same size and roast for a further 15-20 minutes at 200 degrees C.
Remove lamb from marinade and cook on grill plate or barbecue for around 5-8 minutes per side then rest.
Take the marinade and place into a small pan and boil until reduced to a thick consistency.
Slice lamb on the diagonal and serve on warm salad with sauce.