For this cause I Paul, the prisoner of Jesus Christ for you Gentiles,
Note 1 at Eph 3:1: In this verse is a subtle glimpse of one of the things that enabled Paul to endure extreme suffering for the cause of Christ. Paul saw differently than most of us do. He wasn't a prisoner of Rome; he was a prisoner of Jesus Christ. Paul used this same terminology in Eph 4:1; 2Ti 1:8; Phm 1, and 9. In Eph 6:20, he referred to himself in his imprisonment as "an ambassador in bonds."
By just about everyone else's evaluation, Paul was a prisoner of Rome, but that's not the way Paul saw it. It really doesn't matter how other people see you; it's how you view yourself that determines your actions. If Paul had viewed his situation from a merely human perspective, he would have been depressed and probably very fearful. But he had a heavenly perspective. He knew he was a servant of the Lord Jesus Christ, and it was his devotion to the Lord that landed him in jail, not some fault of his own. Therefore, Jesus was in control and not Rome.
The Lord was using Paul's imprisonment to give him an all-expense-paid trip to Rome to witness to the caesar and his entire house (Php 1:13). Paul refused to give Rome or the devil the victory. God was at the controls, and Paul expressed that conviction by calling himself "the prisoner of Jesus Christ."