I own that old LP of Joplin rolls that opens with "Silver Swan Rag."
As I recall, the album notes indeed said nothing about the roll being
Joplin's performance.  That particular volume was otherwise devoted to
period rolls which were heavily orchestrated, bearing little
resemblance to live solo playing.  

I don't have a turntable at the moment for me to check, but I remember
that Silver Swan came across as not humanly played, though perhaps not
as elaborately realized as some of the other rags in the album.  When I
get a turntable again, I'll re-listen to this LP and give a report.

Timothy Tikker