In fact, yes I am. And it is not the helicopter. Although there is a ladder hanging around. Sherlock is checking out the possibilities (the ones that don't work), obviously.
Interesting new perspectives from the roof. It's the first time we get to see a bit more from the window on the left side of the roof (possibly a part of the morgue?) In old times the morgue has been often built in an artrium or inside a building to prevent that people can see through the windows and see something they are not supposed to see. In TRF this part of the roof is intentionally avioded. But for a little glimpse.
 

In the trailer he says he needs to get to know London again...is it part of that?

sirlockofthesher wrote:

He is definitely on Bart's rooftop.

I can't make out if it is before the meeting or after.  I actually watched RF ending and this youtube video a few times switching back and forth.  When Sherlock walks out of the stairwell and onto the roof in RF-look to the left of the screen and you can see the angular-triangular shaped roof.

Here's my take-

The first scene- looks at the ladder on the other side of the building.  I think that is where he is trying to get to.

Then he looks at all the different types of ways he can get to that ladder.  Notice how the circle with the line appears to take out the use of the crane. How he calculates the angle of the pitched roof so that he can get to the "furnace pipes".  And the ladder that appears from the sky-the first images shows a ladder right there on that side of the building...

All of this-shows me- that he physically is getting himself down without jumping...which brings me back to the question-who or what jumped off of that building...because it might not be Sherlock.

(which blows my theory out of the water:-(

Remember the dummy hanging in the kitchen at Baker Street---Henry Fishburn, I believe? (John looks up and says "What'd you do, talk him to death?")

exctly Swanpride, that was also my thought! 

To me, all those mind palace bits seem to be taken into account by Sherlock but finally rejected.

Come on - why should they tell us the solution right now? In the trailer?

sirlockofthesher wrote:

I don't think they showed us the way sherlock got down..
 But I do think they showed us that Sherlock was thinking of a way that had him NOT falling off that roof?  Why look for alternate paths?

Just process of elimination...Jeanette!
(But we still don't know her.)

My take is that he was up there to check how he could get down from that roof top alive before he lured Moriarty there - because that's what he did - and it's simply a part or snippet of the scene where he finally reveals to John what he was doing that night after he'd left him out in the street in front of Kitty's house (I think it was).
By the time he was up there with Moriarty the plan was already in motion. Remember him asking Moriarty for a moment of privacy, I still think that was his moment to check on how preparations were getting on down on the pavement, it simply can't be that he started working out his plan right there at the last moment. He already knew what he was going to do when he brought Molly in.