This was prior to the Crucifixion, Christ later was quite clear when He said, "all nations" (your dispute of that has NEVER been accepted by the Church) and either way, it is irrelevant as there were Jews in Rome.
As I pointed out in post #1467 The wording in [Matthew 28:19-20] "All Nations" has a preferred meaning in the Greek of "All Tribes". You can see it here. The Greek word "Ethnos" is from whence we get our word "Ethnic" and in this case....Matthew is speaking of the Tribes of Israel. Gentile nations is a secondary meaning.
It matters not what the Church accepted....it matters that this would agree with other scripture. [Matthew 10:5-6] [Matthew 15:24][John 21:15-17][Galatians 2:7][James 1:1][1 Peter 1:1-2]
And, of course.....there were more Jews and "other" Israelites elsewhere......millions! These were the circumcised. Gentiles did not circumcise....as a rule.