What did Paul tell the Jewish leaders in Rome about Israel and the Old Testament covenant promises?

Les explains that by Acts 28 Paul had finished his missionary journeys and was imprisoned in Rome. When he called for the Jewish leaders there, he went over again how all the Old Testament covenant promises had been presented to Israel, but they rejected them when they crucified their Messiah. The leaders left in discord and disagreement and could not believe it. Paul then said, 'Be it known therefore unto you that the salvation of God is sent to the Gentiles,' and they would hear it—not that all would be saved, but they would hear. Les notes that Scripture shows the Gentiles have heard, which is why all the world stands guilty and Romans 1 says they are without excuse. With the advent of the Apostle Paul going out, the calling is now predominantly Gentiles—Gentiles only with exceptions, while Jews can become believers but are few and far between. It is a complete flip-flop from Jew only with some Gentile exceptions to Gentiles with some exceptional Jews coming in. Les then points back to Romans 11.