Each of the actors has done other DC projects in different roles.
Stana Katic voiced Talia al Ghul in Batman: Arkham City and Lois Lane in Superman: Unbound
Matt Bomer voiced Clark Kent / Superman in Superman: Unbound and Larry Trainor on Doom Patrol
Elysia Rotaru played 2 different roles on Smallville, Tess on iZombie and Taiana Venediktov in Arrow
Chris Diamantopoulos voiced Green Arrow in the Batman Unlimited film series and Justice League Action
Matthew Mercer voiced Ice Pick Joe on Beware the Batman, Superman & Two-Face on DC Super Friends, Black Arrow, Doll Man & Oliver Queen / Green Arrow on Freedom Fighters: The Ray, a Guard in Justice League: War, Mech Guard #1 & Wealthy Jock in Batman Unlimited: Animal Instincts, Hellhound & Chuckie Sol in Batman: Bad Blood, Anarky in Batman Arkham Origins, Robin in Batman Arkham Knight, Deadshot in Injustice 2, Mr. Freeze in Batman: The Enemy Within and Nightwing in Lego DC Super-Villains
Liam McIntyre played Mark Mardon / Weather Wizard on The Flash and George "Digger" Harkness / Captain Boomerang in the DC Animated Movie Universe
Keith Ferguson voiced Jefferson Skeevers in Batman: Year One, Gruff Cop & Distinguished Man in Batman Unlimited: Animal Instincts, Karate Kid & Nemesis Kid on Legion of the Super Heroes, Superman & Solomon Grundy on Super Best Friends Forever, Alfred Pennyworth & Commissioner James Gordon in Lego Batman: The Videogame and Dr. Stephen Kellerman in Batman Arkham Asylum.