The meeting at Old Trafford ended with a score of 6: 2 in favor of the home team.
Manchester United scored first.
Bruno Fernandes scored in the 9th minute.
Roma responded with goals from Lorenzo Pellegrini, who converted a penalty in the 15th minute, and Edin Dzeko, who scored in the 33rd.
Edinson Cavani leveled the score and put Manchester United ahead with a 48th and 64th minute.
Fernandes converted a penalty in the 71st minute, thus also scoring a double.
Another goal at the 75th and 86th minutes was scored by Paul Pogba and Mason Greenwood, respectively.
The return leg will take place in Rome at the Stadio Olimpico on 6 May.
Earlier it was reported that Villarreal defeated Arsenal in the first leg of the UEFA semi-finals.