Roth? Yes I can understand that. Pentangeli? I don’t think so. He was no threat to Mike anymore after recanting and knowing what would happen to his family if he tried again. Fredo? Absolutely not. There is zero evidence that shows Fredo knew about the plot to kill Mike, there is plenty of evidence to show he was misled and used. Was he stupid? Of course but was it worth killing your own brother? What did it accomplish other than causing more pain for everyone including Mike eventually