It depends on our goals and how we plan the team next season. If want to return to win now mode as we can focus on Serie A without Champions League, Milinkovic-Savic will give a very big boost. With Pogba-Rabiot-Savic-Locatelli rotation will be huge quality for midfield. Savic will be more mature provide goals/assists from mid whom more suitable for Allegri.
With Rovella, we should be patient. He can be 60m player like Tonali but he need time to fits the pressure in big team, gain experience. It's like Tonali after his first season in Brescia, he didnt directly do great in Milan, but need a second season when he finally lived the expectation
Rovella's contract also expiring in 2024. If we dont have plan to play and improve him, there also a chance he will leave like Savic when contract expired. With the package of Rovella (20-25m) + Pellegrini (6-10m) + Money (5-10m), we should be able to give what Lazio wants (40m) and improve the squad now