The singer, 39, will play the role of Persephone in the production, which tells a version of the ancient Greek myth of Orpheus as a singer-songwriter who tries to save his lover Eurydice from the underworld, which is ruled by Hades.
Roberts said: “I am beyond thrilled to be joining the cast of Hadestown in London.
“This show is a true masterpiece, and I am honoured to be a part of such a talented and inspiring team.
“The role of Persephone has such depth and complexity, she feels light and sorrow, joy and darkness.
“Her songs are rich with emotion and an absolute joy to sing, and I’m excited to explore every facet of her character on stage.
“I am grateful for this incredible opportunity, and I can’t wait to share this journey with audiences in London. Let’s take a trip to the underworld together!”
Roberts will star alongside Dylan Wood as Orpheus, Cedric Neal as Hermes, Chris Jarman as Hades and Desmonda Cathabel as Eurydice.
Hadestown, which was first brought to London in 2018, made its return to the capital in 2024 and was nominated for best musical revival at the Olivier Awards that year.
The musical, created by US singer Anais Mitchell, also won two gongs at the WhatsOnStage Awards earlier this year.
Roberts rose to fame as a member of girl group Girls Aloud, which was formed in 2002 on ITV show Popstars: The Rivals.
The group has had four number one singles in the UK with Sound Of The Underground, I’ll Stand By You, Walk This Way featuring the Sugababes, and The Promise.
Last year, Girls Aloud reunited for a UK and Ireland arena tour that celebrated their legacy and paid tribute to their late bandmate Sarah Harding, who died from breast cancer aged 39 in 2021.
On Tuesday, Roberts unveiled a new unreleased version of Girls Aloud song Singapore on BBC Radio 2.
She also told the station “it would be a great shame to not do it (a tour) again” and revealed that she starts rehearsals for Hadestown on Monday.
“It’s very daunting. I went to see the show again on Friday. It’s just wonderful”, she said.
Roberts will play Persephone from September 16 until January 18 2026 at the Lyric Theatre on Shaftesbury Avenue.