Do the roast veggies go in at the same time? HELP!

[Wotsup]

I want to cook a large leg of lamb today for the first time and to put the veggies underneath. If the lamb weighs 2.5kg will the veggies burn? What do you suggest?

I'd put a couple of carrots underneath to keep the lamb out of the fat but not be bothered if they were inedible (can be mashed in to the gravy) I roast potatoes for 45mins so would add them 45 mins before the meat finishes and carrots/parsnips either at the same time or 10 mins after.

Mostly I roast veg in a separate tin, if I' doing parsnips I add a tablespoon of honey to the oil - sounds strange but does work.

Thank you sash. I'll try to follow your tips.