Have Rosencrantz and Guildenstren had any luck discovering what is bothering Hamlet?

In short, no they have not. Rosencrantz and Guildenstern enter a sort of reality of their own. The Claudius and Gertrude have charged them to find the cause of Hamlet's "disteper".Hamlet will have none of it. He has been onto them from the beginning.. "Were you not sent for....?" (Act 2 scene2) In act 3 the two friends tell the King that, "He does confess he feels himself distracted;

But from what cause he will by no means speak." Hamlet more or less plays them with riddles and half truths. “I am but mad north-north-west: when the wind is southerly." There is never any evidence that they ever know what is going on inside Hamlet’s mind and they go to their deaths in relative ignorance.