The song's in the DT here, but without any attribution.
The sheet music I have for Give Me The Roses Now shows R.H. Cornelius and James Rowe as the authors. Is one of them the "Welsh miner" you speak of? I wouldn't swear to it, but I don't think the Carters ever claimed to have written it; they just sang it. I've heard it done by Bryan Bowers, too.