I'm surprised by the need for Intel VROC to get RAID on the NVMe drives. Why can't I just software raid them together?
As Anton said, you can software RAID them in the OS and use any drives you want. Intel VROC is only available on systems with an X299 chipset (and presumably X399), anyway. And apparently there is a list of third-party SSD's
that are supported, depending on which version of VROC the system has.
I also found this bit on the RAID0 support, so apparently it's hit or miss without the key:
An Intel® VROC HW Key is required to use RAID 0/1/5/10 for most SSDs. However, Intel VROC is also designed to provide RAID0 for Intel PCIe Gen3 x8 SSDs without requiring HW key. For instance: Intel® SSD DC P3608 Series. For any other regular x4 SSDs, without HW key, RAID0 might work, might not work. In short, an Intel VROC HW Key is required for official support for RAID0 with regular PCIe Gen3 x4 SSDs. Operating RAID0 in this situation is done at the risk of the user.