I think De Rossi can definitely bring Roma to be even better next season, because the evidence of half a season of coaching at Roma is a very strong benchmark that De Rossi is a coach who has very good qualities. Because, it is rare for a coach to be able to bring about change in a fairly short time. However, De Rossi proved that he only needed a few weeks to make Roma completely change the previous season.
De Rossi definitely wants to achieve better things with Roma in a new season but between his will and final result, there will be differences, small or big only. In the last season, De Rossi came and changed Roma from defensive, counter attacking to mainly attacking in tactics and their team scored many goals, played very goal productive in early matches with De Rossi. After that, honey moon stopped and Roma started to feel difficult to have goals and winnings. At the season ending, result is not to good and certainly is not better than Mourinho's contributions for Roma in two previous seasons.
Because what I know for sure, before Roma was coached by De Rossi, their performance was quite bad, even though they were coached by a great coach like Mourinho.
If you compare Roma position in Serie A when Mourinho was fired and position at the season ending with De Rossi, difference is small.