I agree with you. AS Roma had good results when De Rossi took over as coach of As Roma. And it was a little too late to improve their ranking. This is a pretty good result, they managed to get tickets to the European league next season. With one match remaining, it is impossible for As Roma to catch Atalanta. Poor results with 2 draws and 1 defeat meant they failed to overtake Atalanta. On the other hand, Atalanta is playing very well this season. They could even have the opportunity to qualify for the Champions League if they become European champions. So I think Atalanta has the right to play in the champions league next season.
Bro, as I said before Serie A has 5 tickets to the Champions League for grabs and Atalanta already got one ticket because they finished in 5th place. You need to know that Serie A can actually have 6 tickets if Atalanta win the European League and Atalanta finish in 6th place then one ticket will be given to the team that finishes in 5th place, but in this scenario Atalanta is in 5th place, meaning Atalanta has the opportunity to get 2 tickets to the champions league.
This scenario could happen if Atalanta loses the next 2 matches in Serie A and AS Roma won the last match by scoring 9 goals then AS Roma will take 5th place it's just that this scenario is impossible to happen somehow AS Roma scored 9 goals and match-fixing may be applied, obviously both teams will avoid it.
I do not think there is actually any chance for Roma. First of all, they will have to win the match that they have left with a big goal difference. Secondly, Atalanta will have to lose both of the matches that they have left by a big goal difference in both of them. And I think all of those things are definitely not going to happen. Even if Roma is able to win the next match and Atalanta somehow manages to actually lose the two matches that they have left, I still think that Roma is going to be behind because of bad goal difference. I just do not believe that Atalanta will not be able to take even 1 win of the matches that they have left. And both of those matches are against mid-table opponents, Torino and Fiorentina.