Yakima has a little configurator to show what racks will work with your car. Other companies may have the same. We've had tremendous successful with Yakima and Thule. I'm always a fan of roof racks or hitchracks because they don't move around or loosen. Bikes with slanted top tubes are also much more stable when put into a fork or tray mount. I also like fork or tray mounts because nothing touches the frame/paint of the bike or the car.

http://www.yakima.com/Consumer/Step1.aspx