Mash up 3 or 4 cloves of Garlic with two chopped anchovies and some olive oil to make a paste.
Make little incisions around your lamb leg, push the paste into these incisions and the push in little bits of rosemary.
Rub all over with half a lemon
Cut up veggies (Carrots shallots, potatoes) put them in the roasting tin and place the lamb on top ... follow JAcko's cooking times and foil method.
If you want a really good finish (bear with me it's worth it) , while the meat is resting, drain most of the fat (but keep the juices) from the roasting tray, mash up the veggies, put on high heat on the hob until its sizzling, add a glass of red wine, it will bubble away... whilst its doing this use wooden spoon/spatula to scrape up the bit stuck to the bottom of the tray. Add about 500ml of Lam stock (knorr do lamb stock cubes) stir round, bring to simmer. Then push the veggies and liquid through a sieve into a saucepan to make a thick gravy. Reheat, taste, add salt and pepper as required
Plus either of the above two methods are great