Roof top bike rack?

[dragnusa]

I bought my wife a 02 Jeep Grand Cherokee that I am thinking of getting some roof top bike racks for, I have 4 cross braces on it would like racks that I could attach to them I would prefer something I can put complete bikes on

 

[dragnusa]

Going to need something that will hold cruisers and mountain bikes, plan on getting a hitch rack for the 20 inchers I will have to haul.