Roman Catholic Anachronism
...“Roman Catholicism,” although it is anachronistic for this time period, because phrases such as “adherents of the old faith,” “adherents of the new faith,” “sixteenthcentury Catholicism,” and “early modern Catholicism” are awkward. Also, the Reformers believed they were faithfully representing the Catholic church. Technically, the modification of “Catholic” by “Roman” is appropriate only after the council of Trent (1545–63).
Carter Lindberg, The European Reformations, 2nd Edition (Oxford, UK: Wiley-Blackwell, 2010), 11