Reality TV
Ex-Atomic Kitten singer Liz McClarnon and popstar Jason Donovan will also appear in the production, which is composed and produced by Jeff Wayne.
Roberts will play Parson Nathaniel, a role previously taken by Russell Watson and Thin Lizzy's Phil Lynott.
"My dream has always been to appear in a musical which tours large arenas and I'm very excited to be joining such an incredible cast for The War of The Worlds 2010 tour," said Roberts.
"I am a big fan of Jeff Wayne and I grew up listening to the classic album, so it's very special to be performing one of the main roles of Parson Nathaniel - even more so given that I will share the stage with an 11-foot floating 3D hologram of my fellow countryman, Richard Burton, 26 years after his death!"
Wayne commented: "Rhydian is an incredibly talented singer whose range and depth of voice will suit this role perfectly. I am delighted to welcome him into this year's production."
War Of The Worlds - Alive On Stage! will tour UK arenas in November and December.
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