I think Daniele De Rossi will be talked about well in Europe, it's still too early to tell but I think Roma can fight to get at least to the semi-finals. Of the three teams I've chosen, I think Porto are the most dangerous and as you said, they are tough to beat, and you know that in the Champions League too. Manchester United always start badly lately but then they bounce back, we'll see what they are made of this year.
Roma has been a regular appearance in the Europa in recent times and they have continually made sure to keep up with the struggle to getting the Europa trophy some day, I believe that has influenced the almost frequent change of coach within a very short period of time but importantly is the fact that they have been able to keep their focus on the game and I believe this season they will make better advancement than they had done in previous seasons where they weren't able to get a chance at the trophy, last season was one of the closest they have gone and we are hopeful with Rossi they will do better because since his arrival a lot has changed with Roma and they are appearing like they will do better than they had done last season.
I'm not a Roma fan but I will cheer for them in this European competition, of the Italian teams present they have the best chance of going all the way. I hope De Rossi will not disappoint his fans, their expectations are high but in the Europa League the competition is tight and everyone wants to get as far as possible. I hope well for them