Manager Michael Carrick confirmed the Denmark international would miss the match, despite the encouraging sight of the defender back working with the first-team group on Monday.
Dorgu has been sidelined since suffering a hamstring injury while on international duty with Denmark in September. His last appearance for United came in the 1-1 draw away to Fulham.
The 22-year-old’s return to training had raised the possibility of an earlier comeback, but Carrick made clear that he would not be rushed back into competitive action.
“First day with the group, great to have him back but he won't be involved tomorrow,” the Manchester United manager said.
The club had announced earlier on Monday that Dorgu was back in training, providing a welcome boost after an extended spell on the sidelines. However, the Roma fixture comes too soon for the full-back, who will now continue his recovery with a view to returning to contention in the coming days.
Dorgu’s absence has left United short of options on the left, particularly with Luke Shaw also unavailable. Carrick confirmed that Shaw would miss the European match, while Marcus Rashford’s fitness remained uncertain.
United will therefore have to manage without Dorgu as they look to respond against Roma following their 2-0 Premier League defeat at Chelsea.
The return to group training is nevertheless a positive step for the Dane, whose recovery has progressed to the point where he can begin working again with his team-mates.