Obviously the Europa League is not a priority for any major team. In general, even now in the Europa League, Roma are doing well - they just need to beat HJK and beat Ludogorets in the home game with a difference of 2 goals. In my opinion, this is an elementary task, and by the way, it is far from certain that Ludogorets will be able to score at least a point in the game with Betis.
At the start of this season Roma was surely one of the contender for title, but now things are change, and they are down at fifth spot which is surely still not bad but with their performance they are looking not strong candidate for title they have to do more hard work if they want alive in presence of Napoli, Lazio and AC Milan.
But, here in Europa Cup they still have chance in today match if they beat HJK and Betis beats Ludogorets then clearly they can still stay into Europa Cup otherwise they have to slipped into Conference league which is surely more disgracefully for them Mou doing good things, but their current form is not good, and they need to increase quality as well.
I think that if Roma gets at least in the top 4 (and therefore in the Champions League next year) the season will be recognized as obviously successful. At the moment they are very close to it and they have every chance so I think that Serie A will remain a top priority for Roma.
"So far", when the teams from UCL comes there, they will want to at least win this, because they already upset their fans by not going above the group stage, which means that they are going to end up with something that would be subpar for their talent levels and the amount of money they spent.
In order to keep the fans happy, they need to win this to go on. Look at Barcelona, there is a good chance they will be in europa, which means after spending so much money while in debt and selling big parts of the clubs future, you think anything but a cup win here would be okay for their fans? Hell even financially they have to win to make it worth all the things they did.
Theoretically you are right, but in fact look what happened to all the top teams in the Europa League last year - they were all relegated and didn't even make it to the final (including Barcelona). Maybe this year we will see the same thing, although the Europa League participants can already make a couple of very strong groups for the Champions League, lol.