My poison of choice for removing lettering is ELO (Easy Lift Off, a Poly-Scale product I believe, ie, part of Testors now, check with your LHS). Other choices are rubbing alcohol (get the 91% stuff, not the weaker kind, you may have to ask the druggist where it is in the store) and a pencil eraser, just rub the letters away.
It somewhat depends on the item, but I've never done any Roundhouse cars yet so I can't offer a specific for them, sorry.