Michael: "Hyman Roth has been dying from the same heart attack for the last twenty years."

Is this just a cynical statement or does Michael hint that Roth is faking is diseases? Or does he just mean that Roth is extremely lucky?
On the New Years Eve he obviously has a serious attack. And when he says he can't take a piss without it hurting, it sounds believable. After all, he's a very old man.

Michael probably does realize that Roth is sick, and has been for years.

However that has obviously not prevented Roth from orchestrating several attempts on Michael's life, an attempted takeover of the Family, and a plan to land him in a federal prison.

By the time Michael says that he "has been dying from the same heart attack for 20 years", Hyman Roth is supposedly defeated, weakened, harmless, and looking for a place to live out his remaining days. What Michael is saying is that he really doesn't care how sick or old Roth is...he's still the enemy.

That is it in a nutshell!

Some people will place so much emphasis on a malady of theirs that the people around them become cynical because nothing climactic ever happens.

Years ago, someone posted that Roth's coughs in the "business we've chosen" scene are evidence of congestive heart failure. But, I think he overemphasized his ailments to make himself look weak--no doubt a tactic he learned from Vito.

As for "I'd give $4 million just to take a piss without it hurting": Sometimes I feel that I'd like to have $4M for that purpose...

However, in that particular scene Roth was so angered by Michael's question that it's doubtful he would be overemphasizing his ailments at that point. In fact, it apparently took all the strength he had to get up and respond in the way he did.

I do always marvel at that cough, which was likely a masterful addition by Lee Strasberg to convey how ill the character really was.

One must keep in mind that Fredo's impending murder is in Michael's mind at this time. He cannot listen to reason about Roth, because he cannot murder his brother but let Roth survive.

One has nothing to do with the other.

Whatever his personal feelings about Fredo's fate, that decision had been made. He was now dealing with somebody else.

Roth had done immense damage and had intended to do even more. Michael would've wanted his plane met no matter what his physical condition was.

No. Fredo does not reveal his complicity until several later scenes.

I believe mustachepete is referring to the scene in which the hit on Roth is discussed by Michael, Tom, Neri & Rocco.

In which case, by this time Fredo's complicity is long ago revealed and although supposedly taken back in by Michael his fate is sealed.

Michael is implying that Roth has the habit of exaggerating (if not faking) his maladies as a survival technique.

Not only might that make people underestimate Roth's ability to act decisively, but it may also make his enemies less likely to attack him. Look at how Tom questions the worth of killing Roth when he's expected to die within 6 months

So Roth really could pee?

I knew it.

Whether he could or could not doesn't matter. He's neve part with a million just to take one.