There are several points which have been pointed out already which I won't rehash but a point I haven't seen mentioned is a minor point yet very significant in my eyes.  In Season 1 Episode 23 when Jane and Lisbon are asking Rosalind about Roy T, Lisbon asks Rosalind if anyone else saw Roy and she responds by saying "I have a Fur Elise-olitary life (or fairly solitary life) but she buts specific emphasis on Fur Elise, (the piece of classical music Jane's daughter plays in some of his flashbacks and something that Red John would be aware of). After making the point she makes a particularly satisfied smile, perhaps at the thought that she is taunting Jane without him realising. Otherwise why would she make such a prominent smile over such an insignificant point as saying she leads a solitary life.  The more you watch it back the more obvious it becomes and it seems like the kind of small, well hidden clue, the writer would include, as opposed to something glaringly obvious