The 28-year-old has signed a one-year deal with the club and will provide competition for fellow new signing Ashley Cole at left-back
The 28-year-old arrives on a free transfer after leaving the Rossoneri this summer and has signed a one-year deal in Rome.
The former Ajax man spent time on loan with Premier League club Fulham in 2012/13 after failing to hold down a regular place at San Siro.
“AS Roma announces that it has signed a one-year contract employment contract with Urby Emanuelson,” read a club statement.
“The agreement also reserves the right to extend the contract for another two seasons.”
Emanuelson made 33 appearances for Milan last term, but the 18-time Serie A champions opted not to renew the 28-year-old's contract following a disappointing campaign in which they finished eighth in the Italian top flight.
His capture comes four days after the arrival of former Chelsea full-back Ashley Cole, ensuring competition on the left-hand side of Roma's defence.
Rudi Garcia’s side finished second in Serie A last term, which sealed a return to the Champions League next season.