Preheat oven to 180oC.
Prepare lamb by placing in a snug fitting pan and drizzling with olive oil. Sprinkle over fresh rosemary sprigs and garlic salt. Allow flavours to infuse meat for at least 1 hour in the fridge.
Place in the oven and cook for 3-4 hours for pull apart meat or 2 hours for sliced meat. Serve with fresh lemon wedges, roast potatoes and vegies.