So what does Tessio mean when he says "tell Mikey it was only business. I always liked him?"
Tessio made a mistake in judgement. He had no personal animus towards Michael.
From Tessio's (limited) POV it appeared that Michael was requiring Tessio to take a dangerously weak position towards Barzini's incursions-a position that could only end with Tessio eliminated by Barzini, Tessio forced to accomodate and submit to Barzini or Tessio hounded out of the business completely by Barzini. Tessio made a business decision that now was the right time to jump ship to a "winning team" but it wasn't because he was jealous of Michael or disliked Michael... although he would have overseen his murder...
Michael sums it up perfectly when he tells Tom
"....it was the smart move, Tessio was always smarter."I believe that Tessio played the odds. I don't believe that Tessio's decision was based on any jealousy or dislike for Mike. I believe that it indeed was strictly a business decision on his part.
As for Roth I think that he took the murder of his best friend, his childhood friend, very personally. However he didn't allow his personal feelings to cloud his judgement.
