Why didn't Roth call Ed and ask for a sit down? What would it have hurt? His ego? Shit, his career is on a downward spiral. A VH reunion with him would have given his career the jolt that it needs, to say the least. It would have been great if Roth was back instead of Hagar. But, apparently Roth did nothing while Hagar gave it a shot. Ed had no reason to initiate, he does not necesarily need Roth as much as Roth needs him.
Roth was back in in '96 if he hadn't acted like an asshole. Was Ed totally blameless? I guess not. But, the thing is that Ed is the boss not Dave. Sometimes in life you just have to play the game. Roth had nothing to lose by being low profile back in '96. If you piss off the person who is thinking of hiring/rehiring you chances are you are going to lose.
In a nutshell, Roth can blame only himself.