From what I know, I can only say Eiza Gonzalez has put down a deal to be in the film but other actos who have been contacted by Reeves for roles include:
1. Jared Harris as Dr. Hugo Strange (I even found a cool mock-up of him as Hugo online, kudos to whoever made this)
2. Karl Glusman as Anarky
3. Ella-Rae Smith as Barbara Gordon
4. Jesse Plemons as Harvey Dent (who COULD have an expanded role in Part III)
5. Edmund Donovan as another Arkham crazie turned deranged vigilante by Strange

Also, to address the big one, Joker does return but in a limited capacity that only functions as setup for the third film in which he will have a larger role. It seems Two-Face, The Joker will have secondary villain roles but the Court of Owls (Talon is teased) are the endgame villains for Matt Reeves' trilogy.