This is not really a "theory" but I just re-watched the episode "Red Sky at Dawn" where Red John saves Jane then recites the poem to him.  But... and I think this is KEY.  When Red John briefly comes back to the chair Jane is tied up in, I am sure he closes his lines with:  "Roll Tide."  I rewinded and listened again and I'm very confident that's what he said!
Then... I replayed the episode because in the back of my mind, I'm pretty sure I heard someone say "Roll Tide" during the episode.  Darn it... could not hear/find it again!
Can anyone verify this because it's the type of surreptitious clue that only a "mentalist" would pick up.