I would take pix (esp of the one with severe root rot) and send to the vendor...he should refund or replace.
I've only been to one orchid show, but I bought numerous plants there, from several vendors. I have repotted many, as they were overgrowing their pots. All but two of the 20 or so I bought from vendors had great roots. Of the other 2, one really should have been repotted way sooner, and some roots had rotted...but it had enough left to do fine, so that was OK. The last one was a mess, and when the vendor saw the awful state of the roots (or lack thereof), he apologized and refunded my money immediately. It seems to me your vendo, if reputable, should do the same.