Some of the really big ones have kitchens almost like you would find at home, so in that case the answer is yes. However, even in the smaller vehicles, or in caravans which are quite similar inside, it's perfectly possible to cook a proper meal even if you only have two or three rings and no oven.
In that case your best option is to get a double skillet or similar. These are like two large, deep frying pans which you can clip together to make a small oven. You can use the pans separately for frying, boiling etc, or if they are clipped together you get an oven large enough to roast a chicken and some potatoes, or make a casserole. It should also come with a heat spreader, which makes the base suitable for heating up pies etc. You can even make toast with this.
Apart from this, you only really need a large saucepan for vegetables and a small one, eg for boiling eggs, and you can manage - though a grill is useful, you can manage without one.