Sorry, ReFS is not currently supported. It did not cause a blue screen in our tests, but the format command simply failed to format a RAM disk.
We may implement ReFS support in the future, but in the meantime it's not available. From what we can tell there is little demand for it, since ReFS as a resilient file system designed for physical drives, whereas a RAM disk not resilient by definition (everything is lost on power off or reboot).
We generally recommend using exFAT as a faster alternative to NTFS on RAM disks.