Not totally convinced by that. I suspect Roma's defence (or lack of it) may have helped considerably more. There have been plenty of occasions where they have failed to win and currently sit in 3rd place in the league, so they haven't helped them that much this season.
But why do they have such a good record in the big games? Or when they are the underdog? Surely the crowd must play a significant role? They seem to lose more games against lower sides when the crowd aren’t up for it than they do against the likes of us.