I am a little late on this thread, but have only just returned
from Keswick Jazz Festival where I had the pleasure of pumping many
Joplin piano rolls on a trusty Triumph Autopiano.

The best tempo rather depends upon what you like to hear.  I find
that some play well relatively fast, for example, Elite Syncopations.
Others, such as The Entertainer, sound much more effective at a
moderate pace.  But of course the rolls themselves rather dictate
matters: too slow and the music starts to fall apart and sound far
too mechanical.  I have also heard some played "live" that come over
quite well at a brisk tempo.

Personally, though, I too prefer the Joshua Rifkin collection best
of all.  I found the Nonesuch LPs some years ago and wore them out.
I then got the excellent CD.  Following that I heard Rifkin "live" in
Worcester Cathedral, England, and it was a very special occasion, with
Joplin's best rags given the greatest consideration in terms of tempo
and dynamics -- stately and with feeling to suit the surroundings!

But some of his rags need a lighter approach, and when I am providing
fill-in entertainment at a jazz festival, the folk generally want to
hear something lively and uplifting, to match their happy (and often
merry) state.  So I emphasise the left hand and give them something to
get their feet tapping.  Horses for courses?  Perhaps, but I sell quite
a few CDs and get plenty of requests.

And when I feel serious, I play The Ragtime Dance or Stop Time Rag
at a sensible tempo and give all of the effects that I can.  It's quite
hard to stamp your heel to the beat whilst pedalling!

Roger Waring
Solihull
England