If you are going to use it a lot, go for a receiver hitch rack. You can take it completely off in seconds. If you won't use it much, get a trunk rack. The nicer ones won't scratch your car (much - you will get some micro scratches at the contact points - dosen't show much on white though), and you can take it off. More fiddly though.
IMO a roof rack is nasty looking on a car, OK on an SUV or a Subaru though.
A bra on a car is uglier than any roof rack. Dude, it ain,t a 76 Trans Am.