I don't see why it wouldn't be. Cache drives are just that, caches. They are not used as storage, they just mirror commonly accessed data to speed up reads. Restoring the drive the SSD is caching for should restore the system, then the cache will rebuild itself automatically.
Suggest you send a note to Rollback RX. Depending on how low level are the APIs they use to access the hard drive they might accidentally write around the cache. I think the caching support is mostly software enabled when the software discovers the z68 chipset, not some hardware in the chipset. (That is true of the intel raid0 i use on my x58 MB). If the rollback rx software and the cache software both attempt native disk access something might work funny.