Thornton, who won a Whatsonstage.com Award for playing Adam/Felicia in Priscilla Queen of the Desert, will play Frank 'n' Furter, alongside X Factor's Rhydian as Rocky, Emmerdale actress Pallett as Janet and Superstar winner Forster as Brad.
Oliver Thornton as Frank 'n' Furter
The Rocky Horror Show tells the story of two squeaky clean college kids Brad and his fiancée Janet, who meet Dr Frank’n’Furter by chance when their car breaks down outside his house whilst on their way to visit a college professor.
It's billed as an "unforgettable adventure for them, filled with fun, frolics, frocks, and frivolity, timeless songs and outrageous outfits".
The new revival, which kicked off its tour in Brighton on 17 December 2012, is directed by Christopher Luscombe (Spamalot, Dandy Dick and Blue/Orange).
Ben Forster (second left), with the cast of Jesus Christ Superstar - Tim Minchin, Mel C & Chris Moyles
The musical, which first appeared at the Royal Court in 1973, and was voted "favourite Royal Court Play" in the venue's 50th anniversary year, will play the Liverpool Empire (11-16 February) and the Manchester Opera House (25-30 March 2013).
The Rocky Horror Show features musical classics including "Science Fiction/Double Feature", "Dammit Janet and", of course, "The Time-Warp".
Rhydian shot to fame on X Factor in 2007 before starring in We Will Rock You and Grease; Roxanne Pallett has appeared in Emmerdale and Waterloo Road and took part in Dancing On Ice in 2009; and Ben Forster won the ITV1 series Superstar and then went on to play the lead in Jesus Christ Superstar.