The cable network revealed 12 new cast members for the anthology series. New cast members include Jack Huston, Jessie Buckley, Salvatore Esposito, Andrew Bird, Jeremie Harris, Gaetano Bruno, Anji White, Francesco Acquaroli, E'myri Crutchfield and Amber Midthunder.
Esposito celebrated the announcement on Twitter.
"Now that it's official I can tell you ... I'll be in #Fargo4 !!! Thanks to all of you for supporting me," he tweeted.
FX announced in August that Rock will play the head of a crime syndicate on the show. The season is set in 1950 in Kansas City, Mo., where the heads of two criminal organizations have traded their eldest sons as part of an uneasy peace.
"It's a story of immigration and assimilation, and the things we do for money," a synopsis of the series says. "And as always, a story of basically decent people who are probably in over their heads. You know, Fargo."
Production on Season 4 was expected to begin this year. Series creator Noah Hawley will return as showrunner, writer and director.