Roth always struck me as an extremely egotistical person--probably the most egotistical figure in the trilogy. In Part II, he's always talking about how wonderful their (his and supposedly Michael's) Cuban operations and investments are: "These are wonderful things that we've achieved..." as though they're a bunch of altruistic humanitarians. He seems to love to hear himself talk--like many politicians. Although Vito demanded respect (as we see in the first scene with Bonasera), he didn't have a need to constantly reiterate how great he was. He knew who he was, was happy with it, and that was enough.

Although I have to admit that Roth's joke right before he was killed--"I came home to vote in the presidential election because they wouldn't give me an absentee ballot"--was pretty funny. Making a joke like that isn't a bad way to end your life.