I use isopronanol or perchloroethylene to remove rosin flux if necessary. I even make my own flux with rosin and alcohol. "If necessary" in my book says that it should be cleaned before a conformal coating is applied, as such coatings tend not to stick to rosin very well.
There's no particular reason to clean off rosin flux; it's not corrosive and may in fact be somewhat protective. I've seen radios with rosin flux deposits in excess of 80 years working just fine. Rosin flux is chemically active only when liquefied by high soldering temperatures.
Yes, I know that the electronics chemicals outfits (e.g. Chemtool, GC,...) like to give reasons that rosin flux should be cleaned off, but they're in the business of selling solvents. If rosin flux were corrosive at room temperatures, it would make garbage out of violin strings and gymnasts' hands.'