The duo are the first supporting cast members confirmed for the comic book adaptation, which will see Reynolds reprising his 'Merc with a Mouth' role from 'X-Men Origins: Wolverine', reported The Wrap.
Miller is currently starring in HBO series 'Silicon Valley' and recently featured in 'Transformers: Age of Extinction', while British actor Skrein is taking over from Jason Statham in the upcoming 'Transporter Legacy'.
Both actors are said to be in "early talks" to join the 20th Century Fox film.
Tim Miller, a VFX producer who worked on Scott Pilgrim vs the World, is directing the film.