I've been lurking a few months, sitting on this exploit, making sure it's definitely not old, and I'm quite convinced that it's new and all you BGers will love me for it.
STEP 1: Approach the back entrance of Blacksmith. Be on the right side of the doorway above the small ramp.
STEP 2: Bump up the corner of the doorframe.
STEP 3: While bumped up and walking forward, jump and you should land on the top of the doorframe(make sure to jump forward a second time to make sure you're as far on the frame as possible)
STEP 4: This is where your race is important. If you're a shorter race, mount up. If you're a taller race, disregard this step.
STEP 5: Jump towards the corner shown here. You should land in mid-air. DO NOT MOVE
STEP 6: Once stuck in the air, jump straight up and inch forward during this jump. You should get stuck higher up than you were before.
STEP 7: Run to the side from underneath the corner of the roof, then run straight onto the roof. Congratulations! You're on the Blacksmith Roof no matter who you are!!!
Grats, and good luck owning ground-bound people.
I was sitting on this because I didn't want to see it fixed, but then twinking was ruined, so I no longer care. Enjoy your exploit, community!
EDIT: NOW WITH VIDEO!
[ame=http://www.youtube.com/watch?v=4N_lhKS45a0]On top of BS[/ame]