The intake on the roof is used on many race cars. I think to get ram-air effect engine intake.
Sample:
190. Sports Car Racing in North America: Mid-season 2011 « murphythebear.com
Of course when your engine is in the middle or rear of the car it helps. But it's seen on front engine cars too, with a very useful purpose on road rally or off-road type vehicles (dust and debris avoidance).