I think that Geary and Questadt both thought that the legendary Hyman Roth would never be outfoxed by someone like Mike,and consequently hitched their wagons to a dying horse.
Geary probably figured that he was better off with Roth knowing his little secret,and that he could go back to doing business with "decent Americans". Roth would make the "incident" go away,keep Geary on the payroll,and go merrily on his way while Mike did his perjury(and who knows what else?)time.

Although it is fun discussing this thread,my gut instinct is that FFC just wanted to show Geary as still under the control of Mike and wanting to keep Mike happy by giving his little speech. In my opinion,much like the drapes,and "Michael Corleone says hello",this is one of those things that just went into the final cut with no further thought.

Gotta love it,cause where would be without this kind of stuff to pump up the board?