I agree with you that currently the squad led by Jose Mourinho is still not strong enough, they still have to bring in a few more players to complete positions that have so far been considered to have not given their best performance. True, there is no doubt that Jose Mourinho is a coach who cannot be doubted about his abilities, but still it must be supported by players who can implement their strategies properly.
The first leg of their match will be played at home to AS Roma and in general AS Roma have not met Bayer Leverkusen in any competition for a long time. The last time they met in a match was back in 2015 in the Champions League group E which on a H2H basis for now is still almost even for these two teams. But for this season I have more confidence in the strategy that will be developed by Jose Mourinho because they really want to be in the Europa League final this season in order to win a trophy even though they have to face even tough opponents.
I think Mourinho's quality has been declining for a long time, because before Mourinho coached AS Roma and the truth is Mourinho has failed to deliver good results at several clubs before. So, even though AS Roma is ready to buy some good players in the upcoming transfer market, but I personally don't believe Mourinho will be able to make AS Roma better and stronger.
But apart from that, of course, at this moment Mourinho just needs to focus on finishing the season well. Because after all, at this moment it is also a fact that Bayer Leverkusen is not a weak team because yes, Bayer Leverkusen has managed to improve so rapidly in the Bundesliga as well. Therefore, AS Roma does not have a big chance to qualify for the final, because of course Bayer Leverkusen will try their best to qualify for the final and this match will never be easy for both of them.