Milan had won both Serie A meetings this season, but the Giallorossi's 1-0 success in the second city puts them closer to meeting either West Ham United or new German champions Bayer Leverkusen in the semi-finals.
Match preview
Boasting a recent track record of going the distance in Europe, after reaching two UEFA finals in as many years, Roma's aim of making this season's Europa League decider in Dublin is very much alive following events at San Siro last Thursday.
Having won the inaugural Europa Conference League in 2022, before being edged out by Sevilla in UEFA's second-tier competition 12 months later, the Giallorossi became battle-hardened under former coach Jose Mourinho, and they channelled his spirit to leave Milan with an advantage.
Scorer of the lone goal in the Derby della Capitale just days earlier, Gianluca Mancini headed home in the 17th minute to put Roma ahead, before helping to keep their Serie A rivals at bay until the final whistle.
After finally recording a first win over Milan in 10 meetings throughout the 2020s, the capital club had lost just twice in 16 matches since returning hero Daniele De Rossi took over in January, and speculation persists that he could extend his stay beyond the end of this season.
Occupying fifth place in the Serie A standings, Roma are targeting Champions League football for next term - as things stand in UEFA's rankings, a top-five finish would be enough to achieve that goal - but they could alternatively secure a spot in the expanded competition by winning this year's Europa League.
Such ambitions took a back seat on Sunday, though, as their league clash with Udinese was abandoned when Evan Ndicka collapsed in the 72nd minute and was taken off on a stretcher - the conclusion to that fixture will be scheduled in the coming days.
Now on the road to recovery, Ndicka will watch from the sidelines as his teammates try to finish the job against Milan and then tackle fourth-placed Bologna next Monday.
While Roma breezed past Brighton and Hove Albion in the Europa League's last 16, Milan swept aside playoff opponents Rennes and then Slavia Prague en route to this stage, but defeat last week ended their seven-game winning streak and a 29-match scoring run in all competitions.
Despite having 25 shots at Roma's goal, the Rossoneri were finally thwarted, and after being beaten by old foes Inter Milan in last season's Champions League semi-finals, they now face being eliminated from Europe by another domestic rival.
On each of the last eight occasions they have lost at home in the first leg of a UEFA knockout tie, Milan have ultimately gone on to exit continental competition, so history will be against them ahead of kickoff at the Olimpico.
Held to an entertaining 3-3 draw by Serie A strugglers Sassuolo on Sunday, Stefano Pioli's much-changed side trailed by two goals before Rafael Leao produced a moment of individual brilliance to reduce the deficit, and eventually Noah Okafor's late strike - scored with his first touch after leaving the bench - snatched a point.
Still a distant second in Serie A, they have very little chance of wresting the title away from Inter, who lead by 14 points and can rub salt into the wounds by claiming the Scudetto with a win in next week's Derby della Madonnina.
Milan will want to avoid such a fate, and also beat Juventus to finish runners-up, but winning the club's first Europa League trophy is their major objective between now and the end of this season - however, they must conquer Roma in the Eternal City to keep that dream alive.
Roma Europa League form:
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D
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W
Roma form (all competitions):
D
L
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D
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W
AC Milan Europa League form:
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L
W
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L
AC Milan form (all competitions):
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W
L
D
Team News
After resting Paulo Dybala, Gianluca Mancini and captain Lorenzo Pellegrini for the trip to Udine, Roma will be back to their strongest against Milan, excepting the absence of suspended midfielder Bryan Cristante.
Edoardo Bove could replace Cristante in Daniele De Rossi's starting XI, while Evan Ndicka's setback means that Chris Smalling is likely to return in defence - neither Dean Huijsen nor Rasmus Kristensen were included on the Giallorossi's squad list for the knockout phase.
Ex-Milan forward Stephan El Shaarawy is set to join Dybala and Europa League specialist Romelu Lukaku in the hosts' attacking trident - the latter has scored seven times in this term's competition and 27 overall.
Meanwhile, Milan also rotated their squad on Sunday, but Mike Maignan will start in goal after his absence in Sassuolo, with Fikayo Tomori - who missed the first leg through suspension - featuring just ahead of him.
Simon Kjaer was forced off by a flexor problem at the Mapei Stadium, and Tomori should beat Malick Thiaw to partner Matteo Gabbia at the heart of the Rossoneri's back four.
Tommaso Pobega is back in full training, so Stefano Pioli has an almost full squad to select from: despite impressing last time out, Luka Jovic and Samu Chukwueze - the latter of whom had two goals chalked off by the VAR at the weekend - will make way; Olivier Giroud and Christian Pulisic join Rafael Leao up front.
Roma possible starting lineup:
Svilar; Celik, Mancini, Smalling, Spinazzola; Bove, Paredes, Pellegrini; Dybala, Lukaku, El Shaarawy
AC Milan possible starting lineup:
Maignan; Calabria, Tomori, Gabbia, Hernandez; Bennacer, Reijnders; Pulisic, Loftus-Cheek, Leao; Giroud
We say: Roma 1-1 AC Milan (Roma win 2-1 on aggregate)
The last team to win two away games against Roma in the same season were Fiorentina in 2014-15, and Milan may come up just short in their attempt to do so on Thursday.