In the Europa League, mentality is also very influential because this is a European competition where each match has a different tension compared to the domestic league.
If you look at the strengths, Brighton and Roma don't have much difference, but I can see that Brighton is not a team that has a strong mentality on the European stage, in contrast to Roma.
That's the only thing that differentiates the two teams.
In my opinion, the significant difference in the mentality of teams in such competitions is that less titled teams have increased motivation, and more titled ones have decreased motivation. That is why the favorites here rarely reach the final (and by the way, they don’t worry much about it since the national championship and the Champions League are their priority) and the prize goes to the underdogs.
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.