Cole, who was a free agent after his contract at Chelsea expired, arrived in Italy's capital on Monday to seal the switch.
A statement on the club's website confirming the news read: "AS Roma SpA announces that it has signed a contract with the English footballer Ashley Cole, lasting two years, expiring on 30 June 2016."
The deal includes an option to extend for a further 12 months.
A veteran of 107 caps, the left-back announced his retirement from international football in May after missing out on a place in England's squad for the FIFA World Cup in Brazil.
He claimed eight major honours during his time at Chelsea - including the 2011-12 UEFA Champions League - but fell out of favour under Jose Mourinho last season, making just 15 Premier League starts
In addition to winning three Premier League titles, two with Arsenal and one with Chelsea, Cole has also won the FA Cup on seven occasions.
