You don't have to worry. The Atom processors don't run that hot that they necessitate a fan. As long as you have decent ventilation (a case fan), then you should be good. If you prefer, you can buy a fan for it, and AsRock are decent enough to provide a CPU fan header for such a case. Usually no fan is provided. You can compare to other boards if you wish. These are very popular for using such low power and dissipating such little heat.
In the following link you can see for example how Intel themselves package these processors and motherboards. The heatsink that is without a fan lies over the processor as can be seen in the illustrations in the document: http://www.intel.com/Assets/PDF/prodbrief/320096.pdf