He is known for portraying Lex Luthor on the television series Smallville, a role that TV Guide included in their 2013 list of "The 60 Nastiest Villains of All Time".

[5] His mother, Julie (née Eckstein), is a writer and his father, Mark Rosenbaum, worked in pharmaceuticals.

the Flash) in the DC Comics animated series Justice League, Static Shock, and Justice League Unlimited, as well as portraying a younger version of Wally West as Kid Flash in Teen Titans.

[14] Rosenbaum provided the voice work for Ghoul and Deadshot in the animated DCAU film Batman Beyond: Return of the Joker.

[15][16] He recurred in Fox's original sitcom Breaking In; the show was cancelled initially after the first season but got a second chance, and Rosenbaum was promoted to series regular.

[17][18] In 2014, Rosenbaum made his feature-film directorial and writing debut with the comedy Back in the Day, starring as an actor who returns to his hometown in Indiana for a class reunion.

[19][20] Prior to the production of Back in the Day, Rosenbaum planned to direct another comedy film, titled Sorry is For Sissies.

The plot has been summarised as a "low-life who hides out in a small town by conning the residents into thinking he is their newly hired gay pastor".

[22] In 2017, Rosenbaum served as narrator for the reality television show Hunted which pitted investigators against teams of ordinary citizens trying to evade capture as fugitives.