You can't go wrong with Yakima Racks for a 2008 Honda Fit roof rack setup. The Yakima Q Towers multi-purpose base rack system is ideal for the Honda Fit. No matter what gear you plan to carry on your roof, you will need a multi-purpose roof rack base system. The Yakima Q Tower complete car rack system includes four Yakima Q Towers, two pairs of Yakima Q5 Clips (these Q Clips are specific to your 2008 Honda Fit) and two cross bars. You can then attach any of the various Yakima Racks roof mount gear carriers to the Q Tower front and rear cross bars. The 48 inch cross bars are the recommended length for your roof top.
Here is a pic illustrating a Honda Fit roof rack with Q Towers.
http://www.orsracksdirect.com/honda-fit-kayak-roof-rack.html