Roast lamb with rosemary potatoes

1 leg of lamb
4 cloves of garlic,peeled and sliced
4 springs of fresh rosemary
1kg of potatoes,peeled and diced
500g of carrots, peeled and cut into chunks
2 red onions,peeled and cut into wedge
2tbsp oil
salt and pepper
Preheat oven to 400'f/200'c/gas 6.Put lamb into a roasting tin.Make small slits all over the surface of the lamb and push the garlic and small sprigs of rosemary into the slits.season well and roast for 1 hour.Drain off any fat from pan.
Reduce oven temp to 350'f/180'c/gas 4.In a big bowl put in the potatoes,carrots, red onion, salt and pepper and oil and toss together,put round the lamb and add the left over rosemary.Return to oven for 1 hour tossing veg from time to time.Allow lamb to rest for 10min and carve,serve with the roast veg.