Guys it physically can't be Bertram!  How are people still on this?  He is 6ft 3 and bald which flies in the face of Rosalind's description.  "Under six feet.  Short, straight hair."  Jane COMPLETELY believes that Rosalind's Roy is Red John.  He even took her to the morgue in season 4 to confirm the man he shot in the cafe WASN'T Red John.  Ere go, he trusts her account of Roy as if it were gospel.  Could Bertram wear a wig?  Perhaps but unlikely.  However what is far more unlikely is that he can't cut 4 inches off of his height when he's with Rosalind.  Plus Bertram is a public official who spends waaaayyy too much time in front of the camera.  He would have been easily noticed by Sophie Miller who would in turn probably ask what Jane's boss is doing here.  She would've known right away something was up.  Plus the director of the CBI probably has zero time to go around killing people.  That kind of job requires far too much time at the office and in front of the camera.  A Sheriff of one county is a well-respected official with many friends and quite a bit more freedom to go where he pleases.

Sheriff Mcallister is both marked and a marshall (the whole he is mar thing), fits the height, fits the build "not thin, but not muscular", he loves to hunt/kill as he informed to Jane.  Tom asks Patrick to call him "Tom" because he wants to build a relationship with Patrick, wants to befriend him, as we've seen Red John do with sending him Lorelei  "He's offering the hand of friendship".  In regards to his hair, he had much more 6 years ago when he was cast so Rosalind would have called it "short and straight".

On a side note, some people mention that we never see them physically shake hands... but we do.  In they're very first scene together, they play rock paper scissors, within which you "shake" hands multiple times... :)

Jane: What do you hung?
Tom:  Anything with a face...