During this holding time friends and family were, in most cases, allowed access to the prisoners. Albert A. Bell Jr. writes in his book Exploring the New Testament World, “Some magistrates did gain reputations for treating prisoners cruelly, but this was a matter of individual personalities, not of Roman policy.” The prison systems of today in our culture would be more regulated and be used for holding for trial as well as punishment. The sentence of a 1st century criminal would never be imprisonment. The closest punishment similar to imprisonment would be exile, but as far as we know Paul was never exiled.
Acts 28:16 tells us that Paul was living by himself, most likely in a house, with a soldier guarding him. This description would give more of an idea of house arrest as opposed to imprisonment that we would think of. In Acts 28:20 Paul talks about being in chains, but this was most likely referring to his transport. Prisoners were usually only chained while being transported from one city to another. Acts 20:23 says, “…they came to his lodging in greater numbers. From morning till evening he expounded to them, testifying to the kingdom of God trying to convince them about Jesus both from the Law of Moses and from the Prophets.”
Paul was still able to do ministry work even though he was imprisoned. As a result of these points Bell seems to conclude, “Being ‘in prison’ in ancient Rome begins to sound more like a minor inconvenience than a fate to be dreaded.” I would have to agree with Bell's statement. I'm not sure what the application is for knowing this, but it is always helpful to have as much information as possible when reading the scriptures in order to come to the most accurate interpretation.