Salzburg is probably going to focus mostly on their defense and keep a clean sheet for as long as possible. They have a good squad with a balanced game between offense and defense, but they also that they won't be dominating Roma in a home game. Roma is in quite good shape right now and they have a decent home game statistic so far. Salzburg can wait for their chances while driving Roma to desperation. It's very tough to say who will qualify for the next round. My guess still is that Roma will turn it around.
I don't think Roma would turn it around, Salzburg are a very good team and they played a good first leg, Roma are an inconsistent team, they find it hard to win games in a row, before the first leg many fans thought that Roma were going to win easily, but their inconsistency affected them in the first leg and they lost. The only good thing for Roma is that they are going to play the second leg in their home, so their fans are going to be very loud and behind them, i feel the game will go to extra time and possibly penalties, and if it gets to that, any team can win; but i don't believe that Roma would turn the game around and win during the 90 mins.
Some time has passed but you are right when you say that they are inconsistent. The result against Salzburg was close and the game could have gone both ways. Salzburg was playing well with the ball in many situations, but they didn't use their chances. When Roma scored the first goal I thought that they will exploit the momentum with their fans backing them and that is what they did. I did also think that one more goal will happen when Salzburg is forced to open up.
And just last night Roma lost their game against Cremonse, which is a good example for the inconsistency that you mentioned.