score:4
The primary basis is Acts 28:11β31, part of which is quoted below:
11 After three months we set sail in a ship that had wintered in the island, a ship of Alexandria, with the twin gods as a figurehead. 12 Putting in at Syracuse, we stayed there for three days. 13 And from there we made a circuit and arrived at Rhegium. And after one day a south wind sprang up, and on the second day we came to Puteoli. 14 There we found brothers and were invited to stay with them for seven days. And so we came to Rome. 15 And the brothers there, when they heard about us, came as far as the Forum of Appius and Three Taverns to meet us. On seeing them, Paul thanked God and took courage. 16 And when we came into Rome, Paul was allowed to stay by himself, with the soldier who guarded him. [ESV]
2 Timothy 1:16β17 also indicates that Paul was in Rome:
May the Lord grant mercy to the household of Onesiphorus, for he often refreshed me and was not ashamed of my chains, 17 but when he arrived in Rome he searched for me earnestly and found me [ESV]
Other Pauline epistles mention him being in prison (e.g., Philippians 1:12β14), but don't clearly specify the location.