[Pritcher]

Not very long. I say frame by frame, but you don't have to draw the mask for each frame. You just draw the original one and modify the keyframes where the image actually changes and After Effects handles the 'tween stuff.

Yes though, rotoscoping is extremely tedious work. I only rotoscoped like half that scene then I just drew a simple mask and keyed out all the green for the rest. It doesn't look as clean that way, but it's much faster and it's unnoticeable on YouTube anyway.