FOG itself can create raw images (see Image type after going to Image Management and choosing an image). Maybe someone can give you a more detailed answer.

I have this added to my PXE-menu:
LABEL System Rescue CD “Live Image”
MENU PASSWD m0nd30
LINUX sysrescue/rescue32
INITRD sysrescue/initram.igz
APPEND scandelay=1 docache netboot=nfs://10.187.38.3:/images/sysrescue setkmap=uk
TEXT
SystemRescueCD network boot image (recovery)
ENDTEXT
\n
Then you just need to mount the iso from your OS.