That extra button is up to the skinner,it doesn't seem to be used much any more. Jawndo by Night Train is one of the newer ones to have a Roll Up button.Link You may like it,very polished and a good choice of colors,great for everyday use.Also look at O_Stage_V,also by NT.Link Both are WB6/Vista ready.
There may be a way to add your own with SkinStudio,but that is something I know little about.