The answer to this question depends on our understanding of the verb ἀπειθέω = disobey, be disobedient (BDAG). The word occurs 14 times in the NT. It is never applied to those who have NOT heard the Gospel; it is only applied to:
- People familiar with the Scripture such as the Jews, Acts 14:2, 19:9, Rom 10:21, 11:30, 31, 15:31, Heb 3:18, 11:31.
- People who have heard the Gospel message of Jesus but refused to believe, John 3:36, Rom 2:8, 1 Peter 2:8, 3:1, 20, 4:17.
In Rom 15:31, Paul is quite specific about those he intends by the word ἀπειθέω - the unbelieving in Judea, ie, Jews antagonistic to the Gospel.
After writing this letter to the Romans, Paul traveled to Jerusalem and the series of events are recorded by Luke in Acts 21-26. After arriving in Jerusalem, (Acts 21:17), Paul was mobbed by Jews who wanted to kill him (Acts 21:31).
- Paul was saved from the murderous mob by Roman soldiers saved him (Acts 21:31-36) by being chained and confined to the barracks.
- Again, the mob tried wanted to kill Paul (Acts 22:22) but was prevented from doing so by Roman soldiers.
- Yet again, there was a plot to assassinate Paul (Acts 23:12-15) but this was foiled by Paul nephew informing the Roman commander (Acts 23:16-35) who then arranged for Paul to be taken to Caesarea.
- The Jews tried to arrange for Paul to to be brought back to Jerusalem (Acts 24) by using a paid lawyer at a trial with Felix, but this failed.
There were presumably other attempts by the unbelieving Jews to remove Paul during the two years (Acts 24:27) he was imprisoned under Felix. Later he was tried before Festus and Agrippa (Acts 26) and sent to Rome.
Thus, it appears that Paul's prayer for protection from the Jewish "unbelievers" was answered to the extent that his life was preserved on numerous occasions so that he could preach in Rome (Acts 28).
The Cambridge commentary succinctly observes:
Rom 15:31. that I may be delivered, &c. This prayer was granted, though not in the way expected. See Acts 21:31-32; Acts 23:12-24; Acts 25:2-4;
Acts 25:12.—The words here (cp. 2 Thessalonians 3:1-2,) are among the
many proofs of St Paul’s naturally anxious and sensitive character,
and that his faith and zeal had always this secret obstacle to
struggle with. His life-long victory is the more admirable, and the
more illustrates Divine grace.
APPENDIX - Cause of Antagonism
Barnes makes an interesting observation as to the cause of the Jews' antagonism to Paul in his comments in Rom 15:31 -
That I may be ... - The unbelieving Jews in Judea had been opposed to
Paul's conversion. They could not forget that he had borne letters of
commission from them to persecute the Christians at Damascus. They
regarded him as an apostate. They had heard of his success among the
Gentiles; and they had been informed that he "taught all the Jews
among the Gentiles to forsake the laws of Moses;" Acts 21:21. Hence,
the apostle could not but be aware that in returning to Judea, he
exposed himself to special dangers. His fears, as the result showed,
were well founded. They evinced all the opposition to him which he had
ever anticipated; Acts 21.