"A little help"? Fredo wasn't part of the Havana deal and Michael had no reason to tell him anyrhing about it--he even kept Tom out of the negotiations. Same for Ola: Why would he need to tell Fredo anything more than that Roth and Michael were negotiating "a big deal"? Even if Fredo had overheard or inferred something about Michael and Havana, and if he put that together with Ola's tale, he still couold not have had any details that would have been useful to Roth. So, what kind of "help" could he have given Ola?
I think it's a reasonable inference that he could open the drapes for him.
But, note the subsequent conversation with Johnny: "Will he come alone?...Just go along, everything will be alright FREDO -- PENTANGELI says he's willing to make the deal. All we want to know is if he's on the level or if he's gonna bring his boys...." So Johnny, at least, seems to think that Fredo has ways of gaining insights into the Corleone family that could be helpful to Roth.
Again, though, Fredo's basic character in GF2 is something of a mystery. At the end of the first movie, he seems to be at least useful working in a big casino-hotel. Now the Corleones have four of them, and Fredo's running a brothel. It doesn't make sense. Is the only reason Fredo's doing that in the movie is so Tom can tell Geary it's Fredo's place?
