I don't know. If Ola knew Tom from the "old days" this presumably would have been when Tom was counselor-in-training, right? Tom would have spent a lot of time around Vito just as Sonny would have. Maybe Fredo spent less time on the "inside" than his brothers did but I certainly think Fredo would have known the major players on Roth's side-at least to say hello to.
I'm guessing the old days would have been before Roth relocated HQ to Miami-say 1930-1940 or so.
My thought is that this relationship would run something like Vito to Genco/Tom to Ola to Roth. Vito never trusted Hyman Roth....
