In the Brighton - Roma pair, Roma is the more titled team, so theoretically Brighton will have higher motivation. In addition, I would say that Brighton is stronger than Roma if we compare these teams based on results in the national championships, adjusted for the difficulty of the national championship.
If Liverpool doesn't care and do not play their best players then they may lose this one out too, that is just fine and could very well happen. I would say that it is not going to really be easy for Leverkusen to lose though, they are about to win the league, and the cup is a possibility so if they end up with Europa as well, that would be insane for them. I feel like they have a bigger shot at this than Liverpool if they care about it a lot more.
Liverpool is a different story, they historically try to win all the cups (even small ones) in which they participate. And by the way, given the situation due to Klopp’s upcoming departure, Liverpool could theoretically have increased motivation to win the Europa League since this is the only tournament that Klopp did not win with Liverpool.
Yes, Bayer have a good margin of safety and they can slightly shift their priorities towards the Europa League, but when your opponent is Bayern (even though they are strong only on paper), and you have never won the Bundesliga title, this is quite difficult to do.