I just watched @wendell’s most recent video on the ROMED8-2T, and I have some information about breaking out the OCuLink headers to SATA: according to ASRock Support, just the plain cable will NOT work. Even though my board came with an OCuLink to 4x SATA cable, that configuration is actually not supported (at least back when I asked in November 2020).
There’s more information from when I was initially configuring my NAS with this board over in this thread on the ServeTheHome Forums. I would be quite interested if you did get SATA to work via those OCuLink ports, as that would let me cram a few more drives into my NAS before having to buy a HBA card.
I’m looking forward to the next videos on the ROMED8-2T!