I hope this is better late than never but welcome to the forums!
I'm sorry that it has taken so long for someone to reply to you... I guess that in spite of the overwhelming evidence, a lot of people still believe that Man_Bear_Pig doesn't exist.
As for whether FreeNAS supports Ryzen 3000 hardware, I'm afraid I can't really give you a definitive answer. I seam to remember seeing a few FreeNAS uses running Ryzen but whether they ran into an issues, I can't say. I also remember seeing a few users saying that they were running FreeBSD on Ryzen 3xxx based systems but again, I don't know any details.
Speaking of FreeBSD.... you might be better of trying to find out whether FreeBSD supports the hardware you're looking at as FreeNAS is based upon FreeBSD. Having had a quick look at the latest version of FreeBSD (12.0's) supported hardware, I can say that Ryzen is not listed but that's not a guarantee that it won't work.
I'd advise you to hop over to the forums.freebsd.org and try your luck over there. Good luck!