Let's say he has diamonds in the hole. On 5th he makes a four flush and knowing that only one of his diamonds is dead he re-raises as a semi-bluff. On 6th he pairs his deuce and continues to bet, representing two pair or three of kind and hoping to take the pot down right there. I mean after the re-raise you have to keep betting.

I think it's borderline. I certainly wouldn't berate somebody for folding on the river as you say. But again, I think there's enough of a chance you have him beat that I would call. And Roland did say that this guy seemed "somewhat aggressive."