Cons: Losing a playmaker in the lineup
If one of Herro or Rozier comes off the bench, the starting lineup would be Rozier/Herro, Haywood Highsmith, Jimmy Butler, Nikola Jovic, and Bam Adebayo. It's a lineup full of playmakers plus an outstanding defender in Highsmith.
One could argue that there's enough playmaking on the floor with the group and that the defensive upgrade in Highsmith is needed. That point has some validity, but there are still moments when a plus defender like Highsmith could be played off the floor if he can't make teams pay for leaving him open. Teams would never dare to purposely leave Herro or Rozier open as they've created reputations as big-time shotmakers.
The numbers suggest that Herro and Rozier haven't offered a great playmaking punch in their limited time together. According to Cleaningtheglass, Herro, Rozier, Highsmith, Butler, and Bam were -5.7 in 119 possessions together. Again, this is a very small sample size, but staggering the backcourt seems to have more pros than cons.