This looks somehow to me because I'm trying to understand if it's Lazio and fiorentina that has performed below average that will be able to replace Roma even if I know Roma hasn't done any better tho but Roma is more considerable then you will with fiorentina, Lazio is performing below their known performance last season but the are still at a fair position on the table.
If Rossi is consistent enough even if he's new but he's started on a very good not and if he's consistent not loosing any game further, even with a draw he can be sure to help the team stay at the fourth position and secure a champions league spot for next season. Lazio is the next with such chances but it still depends on their performance. Bologna hasn't be really bad and can possibly displace Roma but they will have to find a weakness for Roma upon which they will take advantage and see to displacing them to secure the fourth position and aswell a spot at the UCL.
Sometimes a change of coach can have a positive effect on the mood of the team, but often such results are temporary. It’s still too early to evaluate De Rossi’s success, and it’s still too early to evaluate that Roma was able to get closer to the top 4, Fiorentina, Lazio and Bologna have one game in hand, and each of these teams has a chance to get ahead of Roma. But if Roma can continue to play this well then they will have enough time to climb into the top 4 as Atalanta is very close.