As a character Rosita has been vastly underutilized. In season 7 she finally got to show some character development as she grieved for Abraham and took Sasha with her on her suicide mission to kill Negan.
Some interesting information about her past was revealed when she told Sasha where she learned about explosives and other things. And just from those little bits of information it’s pretty clear that a prequel of Rosita’s journey from the beginning of the apocalypse until the time she met Abraham would make for a great spinoff.
And her journey could even possibly be tied to the developing story on Fear The Walking Dead, since that group ends up in Texas and Rosita is from that area. There is a lot of Rosita’s backstory still to be explored and it doesn’t look like that exploration is coming anytime soon on The Walking Dead.
Rosita is also one of the few characters that could carry either a prequel type spinoff or a sequel spinoff after the events that have occurred in The Walking Dead. After All Out War is finished it would be easy to see her deciding to head out on her own because she doesn’t have any strong relationships with the core group and she may decide to take her chances somewhere else.