6 Among whom are ye also the called of Jesus Christ.
The Romans were new Christians who probably didn’t understand everything their salvation did for them. So Paul explains.
“Called” = An invitation given by God and responded to. Two verses with a parallel usage are:
Matthew 22:14 — For many are called, but few are chosen.
Revelation 17:14 — These shall make war with the Lamb, and the Lamb shall overcome them: for He is Lord of lords, and King of kings: and they that are with Him are called, and chosen, and faithful.
Those who trust Christ aren’t saints by their own devices, but due to a calling by God — just as Paul didn’t appoint himself an apostle.
Romans 1:1 — Paul, a servant of Jesus Christ, called to be an apostle …
Romans 1:6 — Romans are … the called of Jesus Christ.