Well that's your own opinion on the match, although Milan is ahead of Roma but I think with the recent playing strength from both teams it will be very hard for Milan to win the tie especially not with the way Roma have being scoring and again let's not forget that the champions league is a totally another world and atmosphere entirely and some times most teams do extra well when playing a game here than that of their league.
I think it makes sense if he favors AC Milan because AC Milan has perfect results in the last 5 matches in Serie A. They won all the matches, it is a positive sign for the match against AS Roma in UEL match. However, I don't deny that the performance in domestic competition sometimes won't guarantee the success in international competition such as in UCL and UEL.
I know what's your point. AS Roma becomes a stronger team under De Rossi's management. They are not easy defeated by any team now, they could play as a solid team nowadays. But De Rossi seems to have no much experience as a coach, he still needs time for adaptation. For example in Serie A, AS Roma got a draw against Lecce in matchday 30. Meanwhile AS Roma could destroy Lecce with 3 goals in matchday 31. It simply showed the different of level between AC Milan and AS Roma. It also showed the ability of both the coaches.
So, I think AC Milan looks a bit better and has a higher chance for qualifying for the next round.