Another vote for parboiling potatoes - but to be more specific, put potatoes in cold water, bring to boil and allow to boil for 3 mins. Drain, put lid back on saucepan and bash them around a little, then chuck into hot oil (if there is room in the meat roasting pan, this is perfect). Cut up peppers, mushrooms, onions, sweet potato, butternut squash, garlic and put in another roasting tray with some olive oil and if you like it fresh rosemary and/or thyme - roast in oven for about 30 mins. Cut carrots into battons and put in ovenproof dish with a knob of butter, and cover tightly with foil. So far everything is cooked in the oven. If you want to boil vegetables on hob, reserve the cooking water and use to make gravy - use bisto powder.