That scene of Roth's soliloquey (one of the best in the Trilogy, IMO) shows two deadly, dedicated predators playing out their end game as the clock ticks down:

--Michael had only hours left to find out who the traitor was in his family before Roth would make his move to assassinate him after the New Year's Eve party;
--Roth had only hours left to wheedle the $2 million out of Michael before having him killed.
--Both of them knew, or were reasonably suspicious, that the other was onto their game.

Michael started by trying to force Roth's hand ("I...just wanna wait..."). Seeing that his seeming indecision made him look weak in Roth's eyes and might make him vulnerable to a demand to hand over the cash immediately, he tried to put Roth on the defensive ("Who had Frank Pentangeli killed?"). But Roth parried him brilliantly with the Moe Green rap. So, in a large sense, the exchange was tactical: the final moves to keep their relationships going in order for both of them to buy more time.

But, to the original point: I believe Roth was saying that he took Moe's murder personally ("As much as anyone, I loved him, and trusted him..."). But he also acknowledged that Moe was "headstrong, talking loud, saying stupid things. So when he turned up dead, I let it go...I didn't ask who gave the order because it had nothing to do with business." There, I believe, he was rebuking Michael for the new, harsh tone in his voice when he demanded to know who had Frankie killed, and for the implication that Michael took it personally.

Another point to keep in mind: The last thing Michael said to Roth in Miami was, "Frank Pentangeli is a dead man." So, in Havana, was telling him that the Rosatos' murder of Pentangeli was business that Michael himself had sanctioned--another rebuke.

What a brilliant, complex exchange!