By using some coding (hopefully easy) or some MPQ programs, you can make your own mpq and, replace the war3.mpq with your own mpq. Just get everything from war3.mpq, extract it, put it into a folder, put everything that is custom or Frozen Throne in, then rename it into War3.mpq (warning: get the real war3.mpq into a folder for backup. Of course, you can always reinstall. Hope this helped.
EDIT: However, if you want an easy convert, then go to map description to show you why the map can't be played in Reign of Chaos, and then change the things. Also: I can't remember if ROC has a import thing, but I heard that there is something for it.
EDIT 2: Thanks for the rep! No problems.