Well, I don't know what you are going for, what software you have or how much time you want to spend. I just watched something on the chroma keyer thing yesterday, so I wondered...
Place a camera in the car and say you want the car to roll over. So, you get the people in the car and setup how you want everyone to act and then you record it. Here is where the chroma feature things comes in that I dunno if it would work, but could you put green paper in the windows of the car, then take video outside a way from the car and roll (actually roll the camera to create the effect) shooting nothing but the background. Then in FCP make that video superimpose over the original shot on the green paper using the chroma keyer thing. This might be a stretch, but it would look cool.
If not this, then just show the driver getting all scared and thrown around without actually showing the car. Then just adjust the speed of the video to create the desired effect. Maybe after the wreck you could muffle the sound and show the person in a bit of shock etc.