United were denied only their third win on Italian soil by Alessandro Mancini's leveller at the Stadio Olimpico, but once again violence scarred the Red Devils' trip to Rome.
A 16-year-old United supporter is believed to be among seven fans who required hospital treatment following trouble before the game.
For the second season running, off-field problems overshadowed an enterprising contest, with Gerard Pique putting a youthful United line-up in front with a neat first-half header.
Captain Wayne Rooney and Michael Carrick were the only two players who retained their places after Saturday's 4-1 win over Derby as Ferguson gave his youngsters valuable Champions League experience in the Stadio Olimpico.
Both sides had chances to snatch it in the 90th minute. First, Nani's poor chip fell straight into the arms of Doni before Vucinic blasted his volley over from three yards.