The former Two and a Half Men actor will play the President of the United States in the Grindhouse movie sequel starring Danny Trejo and Michelle Rodriguez.
Robert posted a photo of himself with Sheen on Twitter, writing: "I just cast Charlie Sheen in #machetekills as the President of the United States! Who better? More soon..."
Sheen retweeted the news, with the introduction: "My Fellow Americans!"
Mel Gibson joined the film earlier this year as an eccentric billionaire arms dealer hell-bent on launching a deadly missile.
Jessica Alba, Zoe Saldana and Amber Heard have also signed up for the movie.
Sheen is currently promoting his new FX sitcom Anger Management, loosely based on the 2003 Jack Nicholson film of the same name.
The 48-year-old has claimed that he plans to retire from acting after he finishes Anger Management.
"At some point you just get tired of wearing somebody else's clothes, saying somebody else's words and working in somebody else's space," he said.
Anger Management debuts on Thursday, June 28 at 9pm ET on FX.
Watch a trailer for Robert Rodriguez's Machete below: