The Argentina international is still recovering from a shoulder injury which has kept the centre-half sidelined since early December.
Daley Blind and Chris Smalling formed United’s centre-half partnership and managed to keep a clean sheet despite Emre Can and Roberto Firmino testing David De Gea.
England and Red Devils captain Wayne Rooney scored the winner with 11 minutes remaining to extend United’s unbeaten run to three games in the Premier League.
And Rojo posted the above photo with his friend after soaking up the Anfield experience on Sunday afternoon.
Rojo wrote: “Important win great game and very good experience with my brother at Anfield”
United are in fifth place and two points behind fourth-placed Tottenham Hotspur in the Premier League table.
Louis van Gaal’s side host Ronald Koeman’s Southampton side in their next Premier League game at Old Trafford next Saturday.
MORE: Man United latest news
MORE: Arsenal latest news
MORE: Chelsea latest news
MORE: Liverpool latest news