Leverkusen yes, but I don't see Roma being on the same level. In my opinion Roma is not even close. They improved their game lately, but there is still a huge gap when you compare them to Liverpool. But I think we will get to see a nice test when Liverpool now plays against Manchester City. That's the toughest test a team can have.
However, I think in a final everything is possible. If Roma can manage to make it into the final, then I wouldn't assume that they are without chances. Playing a final is always different from playing league games.
In the European League, some teams can show different performances than in their domestic league, that's why we see surprises more often in this competition. I agree with you, even though Roma have experienced an increase in performance, they are not yet on par with Leverkusen and Liverpool, even though they were finalists last season and are now starting to appear impressive.
Liverpool are in a safe position to continue the second leg match, because their margin of victory is quite large, while Leverkusen have to try a little harder to win after being held to a draw by Qarabag. These two teams deserve to be favorites, and Liverpool will again shift their focus to the Bigmatch against Man City in the EPL.
On the other hand, I still hope Milan can do something impressive in the Europa League, even though we know they are not as consistent as Liverpool or Leverkusen. At least the European League will become more fierce if Milan becomes one of the teams challenging for the title. Even though he is also in a safe position, Pioli must be able to improve his fleet defense so that they don't concede easily in the next match.