I have no doubt that Mourinho is a very experienced coach. However, Roma's squad is not strong enough. If the Roma management had made a bigger fund and given Mourinho full freedom to build his squad with the players of his choice, the Roma team would have been stronger.
However, Roma's performance this season has been quite good.
They have better performance than the past season but it seems they are starting to be exhausted in ending weeks of season. Many players are injured and Roma squad as we all know, is not deeply enough to have replacement but still maintain their general strength.
Roma attacking system depends on Dybala a lot and it is worse as they temporarily have many defenders injured recent weeks and have yet recovered. Their success in Serie A and Europa League will be decided by alternative defenders in some rest matches.
Their opponents in the Europa League semi-finals are Leverkusen. This team is in pretty good form right now. But their defense is weak. If Mourinho is able to identify Leverkusen's weaknesses and create a good match strategy, Roma should be able to win against Leverkusen.
Roma will surely play carefully and defensively with intention to block Leverkusen attacking and wait for chances from counter attacking. They will have to hope that Dybala will be ready for those semi finals with Leverkusen. Without Dybala, their attacking system will have less creativeness that decreases their ability to score goals.