The two sides took commanding leads in the first legs, leaving onlookers in no doubt as to who was favourites to go through.
Whilst Liverpool were irresistible against City, Roma could count themselves unfortunate as a pair of own goals appeared to put paid to their hopes of progressing.
A difficult result to overturn
In the history of European competition a 4-1 first leg result has only been overturned 18 times and just four times since the year 2000. Those stats suggest that Barca have little to worry about on Tuesday night.
Celtic were the last team to overcome a 4-1 first leg deficit, going down by that scoreline against Legia Warsaw in Poland in qualifying for the 2014-15 Champions League, only to claim a 3-0 win at home and progress.
To find the next most recent example we must cast or eyes back considerably to the Champions League quarter-finals in 2003-04, and Deportivo La Coruña's famous victory over AC Milan. The 'Rossoneri' eased to a 4-1 win in the first leg, only to be stunned in Spain as Deportivo claimed victory by four goals to nil.
The other two times that teams have come back from the result since the turn of the century both took place in the UEFA Cup. In 2001-12, Club Brugge beat Lyon 4-1 in the first leg of a last 16 clash but were eliminated after a 3-0 defeat in the second leg.
And finally, an infamous result in the history of Spanish football saw Real Zaragoza eliminated by Wisla Krakow in 2000-01. The Spanish outfit crashed out on penalties following a 4-1 defeat in Poland after winning 4-1 on home soil.
Easier for City
If we analyse Liverpool v Man City in more detail, whilst a 3-0 win may at first glance appear more convincing than a 4-1, statistically speaking it is actually easier to overturn, with 30 teams having come back from being on the receiving end of result in the first leg to qualify, though as with the Barca result, the majority of these took place before the year 2000, with just five occurring since the turn of the century.
The last time a comeback from 3-0 took place was in 2013-14 when Valencia bounced back from from a 3-0 loss to Basel in Switzerland with a crushing 5-0 victory on home turf. That wasn't the first time they had come back from that scoreline either, hacing produced a 4-0 win in the Europa League qualifying round to stun Swedish side Gelfe.
Looking further back, in 2004-05,Cypriot side AEK Lanarka thought qualification was a formality following a 3-0 win in the first leg, only to lose the reverse fixture 4-0 to Maccabi Petah Tikva in UEFA Cup qualifying.
As well as these examples from Europe's second best club competition, there is also one example of the deficit being overturned in the Champions League since 2000. Once again this came in the qualifying rounds in 2003-04 as Albanian outfit KF Tirana matched Dinamo Tbilisi's 3-0 in the second leg before emerging vitorious 4-2 on penalties.
The final example of the comeback since the year 2000 was in the qualifying rounds of the UEFA Cup in 2001-02 as Estonian side Narva Trans lost 5-0 to Elfsborg in the second leg after winning the first game 3-0.