Roma is not that strong and they're not stable but if they take this match very serious, they can achieve victory. Porto isn't a strong team too and I believe that whoever among these two clubs that can outplay the other will definitely qualify to the round of 16. I will both clubs have the same strength and it's a perfect match.
Even last season when Roma was in a preferably better form than they no, I wouldn't have considered them as better and place a bet on them to win Porto, not like they have got a really good depth, they are even seemingly looking like they have got almost equal strength with porto and would most definitely not have it easy playing against Porto but then if they turn out the better side at the end of the day, we can be sure to say they may get lucky enough to win the game and probably have that advantage to staying ahead hopefully by the end of the game.