Well, the option to boot from USB should be in there somewhere according to the manual (http://dlcdnet.asus.com/pub/ASUS/mb/SocketAM3+/M5A97-EVO_R2.0/E8045_M5A97_EVO_R2.pdf --> section 3.7, page 3-32).
Without actually using the motherboard for myself, I can't really help any more than this. Maybe someone with this board can chime in.