Well, this episode just continued the trend of season 6 so far.
Eliminate one suspect on the list after another, until no one is left.
So RJ could basically be ANYONE.

If we take the list:
Partidge: dead (but we never saw the face of the body, Cho inspected)
Kirkland: dead (for sure, but what about the twin brother?)
Stiles,
McAllister, Haffner: dead (but not confirmed?, only thing we saw was
their pictures on the wall and a foot on the ground at the scene. Jane,
Smith and Bertram survived, so why not someone else?)
Smith: in custody
Bertram: alive, on the run.

So it is Bertram, right? Well, no. Bertram wanted to kill Jane, because he knew about Tyger, Tyger.
PJ is driven by his hate for RJ. He wants to take revenge. Jane wants to
kill RJ, not have him arrested. So why tell the media RJs identity, so
that every law enforcement agency is on the manhunt for him? Right, he
wouldn't. He wants Bertram arrested, because he is a high ranking member
of Tyger, tyger.

So where does that leave us?
I really, don't know, but there is still a major plot hole, that hasn't been revealed.
What about the gunshot before the explosion and the explosion itself.
Who fired a gun? Was anyone shot?
And
who set of the bomb? If it was RJ, why would he set up an explosion,
while being in the room? He would have to calculate a possibility of
dying himself, by doing such a thing/ And suicide sounds nothing like
anything RJ would do.
So the assumption would be, that RJ was not in the room.
So
that leaves a couple of dead persons (Partridge, Kirkland, the twin,
even Bosco [they showed his dead again, shot in the ribcage, a shot you
could survive...], or the new detective or Mashburn or.., or...).

I
am not going to make a pick here, because throughout the show I have
been 100% certain to know who RJ is so many times (from Stiles to La
Roche to Partridge to Haffner and back and so on) and one episode away from the reveal, I am clueless again.

Who
I want it to be: Partridge, because Jack Plotnick is a terrific actor
and portrayed Partridge the way I would imagine RJ to be. Highly
intelligent, skilled and icredibly creepy. But it is so very unlikely he is still alive and RJ.