If your motherboard is prepare to recognize RAID configurations, it is possible to create the RAID volume from control-I menu (from start up), without Intel® Rapid Storage Technology. Asus and Gigabyte motherboards allow to create the RAID from the BIOS.
Go to your motherboard manufacturer website, download and install the latest drivers and BIOS for your motherboard including the iRST. If you want to have more drives in your computer, you just need to plug them with the SATA ports. The system will not include them as part of the RAID volume.