This guide will teach you how to get up onto the roof of the inn at Freewind Post, the Horde Town in Thousand Needles.
As you come out of the inn, turn right and walk to the right hand side of the building. There should be two wooden 'beams'. You need to go up to the side of the one nearest the door, but on the side facing away from the door. Then, you simply need to use the jumping up corners technique to get to the top of that 'beam' thingy. I'll warn you that this is MUCH harder than any previous wall jumping up thingies, so it might take a very long time for you to get up there.
When you finally reach the top of the 'beam' thingy, jump onto the relatively falt bit of roof and you're there
Have fun
As an alliance you could do this to snipe off the guards or other players withouyt them reaching you