I also favor Fenerbahce to win this match. Although United is an EPL team but their performance is very inconsistent. They can compete with big teams in the EPL but they can also lose surprisingly to mediocre teams. In this match Fenerbahce is playing at home so that will give them motivation. Jose Mourinho is also an experienced coach who can give Fenerbahce a win.
If Manchester United got defeats from Premier League clubs that are not big clubs, they can lose to a club from another league like Fenerbahce. They are playing in Europa League with clubs from many nations and domestic leagues, it is even more challenging than playing against clubs in Premier League. Because Manchester United can have more information and past experience with opponents from the same league, but with opponents from other nations like Fenerbahce, there is lack of information and past experience, so there is bigger chance for surprise from Fenerbahce.
If you look at Roma's statistics I agree they are still struggling to score goals. Roma are not very good at attacking and they are also not very solid in defense. On the other hand Dynamo Kiev has been consistent in the league although of course Serie A has a much higher level than the Ukrainian League. But overall it seems Dynamo Kiev is much better than Roma.
Roma have problems in both attacking and defense and after recent bad results, any match from now will be like a final match for Roma coach. He can lose his coach position anytime because so far, he did not show that he is performing better than De Rossi, whom was sacked weeks ago.
Again Roma can lose this match like Manchester United even they are both from bigger and better leagues, Premier League and Serie A. If Roma lose to Dynamo Kiev, it won't be a big shock with their terrible form recently.