You can try inserting the modules for RAID into the core.img file that grub2 uses.
boot from the DVD and select rescue mode, this should mount your installed system under /mnt/sysimage
edit your /mnt/sysimage/boot/grub2/grub.cfg and add the lines:
Then (If you are using the first 2 disks in your system for your RAID)
/boot does not have to be a non-RAID partition, but sometimes even with inserting the modules manually it doesn't work properly. So it is stilll recommended to have /boot on a non-RAID partition.