Hammer was cast as former White House counsel John Dean, but was forced to withdraw from the project amid a sex and texting scandal earlier this year (21).
The "Call Me by Your Name" star is currently under investigation in Los Angeles following allegations of sexual abuse.
"Gaslit" is based on the Slate podcast series "Slow Burn", which focuses on the untold stories and forgotten characters of the Watergate scandal, which ended Richard Nixon's U.S. presidency in the 1970s.
Roberts is among the executive producers, alongside director Matt Ross.
The scandal emerged, months after the actor and his wife, Elizabeth Chambers, announced plans to divorce after 10 years of marriage. They share two children and their separation was allegedly caused by his infidelities.
When the actor was first hit with scandal, he initially insisted, "I'm not responding to these bulls**t claims." As more accusations piled up, he began to rigorously deny any wrongdoings.
He was recently accused of rape by a former lover he met on Facebook. The woman has turned evidence over to Los Angeles Police Department officials.
While the star didn't deny his past hookup with the woman, he insisted it was consensual.
His lawyer stated, "Her own correspondence with Mr. Hammer undermines and refutes her outrageous allegations. As recently as July 18, 2020, (Effie) sent graphic texts to Mr. Hammer telling him what she wanted him to do to her. Mr. Hammer responded making it clear that he did not want to maintain that type of relationship with her."