Roma still has a match against Milan today and also Venezia before facing Porto. Facing Porto will not be easy, but Roma's performance is also sometimes surprising and very difficult to predict.
If in the first leg, Roma manages to hold Porto to a draw, I am a little optimistic that Roma will advance to the next round. But if the situation in the first leg is bad for Roma, then it will be difficult for them to create a chance to advance to the next round by winning the second leg.
I assume the match against AC Milan not too important for Roma because this is only Coppa Italy match so i think Ranieri will do a rotation to Roma squad for this match and i think they will be more likely to focus for the match against Venezia because if won from this match it can improved their position on Serie A
Actually the owner didn't set high target to Ranieri so if Roma failed to get the trophy from this competition Ranieri position as a manager still safe at least at the end of this season but i think Roma will considers the match against Porto is important too
Roma performance when they beat Frankfurt is very impressive and in Serie A too their performance is getting better so they might be will make Porto get in trouble and for the first leg i am sure Roma will attempt to get draw result and if possible won from Porto
If Roma manages to beat Porto, it will be good for Ranieri who might have a chance in the next round to advance further in the Europa League. And for Serie A, although there is no target for the trophy, at least Ranieri must push Roma's performance to rise in the standings. At least they must occupy a position where they get tickets for European competitions.
Roma's points difference with the teams that are at least in the top 6 of the standings is quite far. So it takes a lot of effort to be able to push Roma up the position.