This is a clearer description of the Rundown Cantina Roof.

Go up the stairs, climb into the window frame, look left. You want to push forward and fall onto the small sign there. You must go full speed without running, then, as you fall onto it, pull back so you don't run off of the sign. It is a bit tricky, but comes easily with practise.

The black ironwork that the sign hangs off of is fake, don't go too far out from the building, remember that only the sign is real. Once on this small sign, look left at the very corner of the roof that runs down the side of the building, jump to it.

Good luck.