The Argentine international had been on the sidelines since suffering knee ligament damage in United's Europa League clash with Anderlecht back in April.
The centre-back played 45 minutes of the Premier League International Cup against Athletic Bilbao earlier this week, and will now be in the squad for Saturday's Premier League game against Newcastle United.
"At last finally the day came. I want to first of all thank my wife and my two children that were always with me in this difficult time," Rojo told reporters.
"I want to thank all the people at the club Manchester United who have been with me since day one. Thank you all very much. Happy to have this feeling of playing on the pitch again. Now I continue working."