Thule and Yakima make great bike racks. They both have roof mount styles where both wheels can be kept on, or styles where only the fron wheel must be removed.
There are a lot of people out there that make bike racks. So depending on what style you want there are a variety of brands including Thule, Softride, and Yakima.
Bike racks come in many types- Some hang off the back of the vehicle, others sit on the roof. Questions like MPG and expected drag will come into play.