Question: When did the English rock muscian and former Pink Floyd bassist release his fourth studio album?

Context articles: Wish You Were Here (Pink Floyd song)
Déjà Vu (Roger Waters song)
Radio K.A.O.S.
Barrett (album)
Is This the Life We Really Want?
Smell the Roses
Opel (album)
Ça Ira (opera)
The Final Cut (album)
What God Wants, Part I

"Wish You Were Here" is the title track on Pink Floyd's 1975 album "Wish You Were Here".
 Like most of the album, it refers to former Pink Floyd member Syd Barrett and his breakdown.
 David Gilmour and Roger Waters collaborated to write the music, and Gilmour sang the lead vocal.
"Déjà Vu" is a song by English rock musician and former Pink Floyd member Roger Waters, and the second track on his fourth studio album, "Is This the Life We Really Want?
" It was released as a single on 8 May 2017, with the album being released on 2 June 2017, by Columbia Records.
 It was previously known as "Lay Down Jerusalem (If I Had Been God)" when played live before single's official release.
Radio K.A.O.S. is a studio album by English rock musician and former Pink Floyd member Roger Waters.
 Released on 15 June 1987 in the United Kingdom and June 16 in the United States, it was Waters' second solo album after his split from Pink Floyd in 1985.
 Like his previous and future studio albums and many works of his during his time with Pink Floyd, the album is a concept album that is based on a number of key factors of politics in the late 1980s, including monetarism and its effect on citizens, popular culture of the time, and the events and consequences of the Cold War.
 It also makes criticisms of Margaret Thatcher's government, much like Pink Floyd's "The Final Cut", another album conceived by Waters.
 The album follows Billy, a mentally and physically disabled man from Wales, forced to live with his uncle David in Los Angeles after his brother Benny was sent to prison after protesting against the government, following his dismissal from his job in mining due to "market forces".
 The album explores Billy's mind and view on the world through an on-air conversation between him and Jim, a disc jockey at a local fictitious radio station named Radio KAOS.
Barrett is the second and final studio album of new material released by former Pink Floyd frontman Syd Barrett.
 Recording began at Abbey Road Studios on 26 February 1970, and lasted for 15 sessions until 21 July.
 The album was produced by Pink Floyd's guitarist David Gilmour and keyboardist Richard Wright, who also contributed on bass guitar and keyboards respectively, along with previous "Madcap" contributor Jerry Shirley on drums.
Is This the Life We Really Want?
 (stylised as is this the life we really want?)
 is the fifth studio album by English rock musician and former Pink Floyd bassist and vocalist Roger Waters, released on 2 June 2017 by Columbia Records.
 It is his first solo album in nearly 25 years since "Amused to Death" (1992), as well as his first studio album in 12 years since "Ça Ira" (2005).
 On 20 April, the single "Smell the Roses" was released.
"Smell the Roses" is a song by English rock musician and former Pink Floyd member Roger Waters, and the ninth track on his fifth studio album, "Is This the Life We Really Want?
" It was released as a single on 20 April 2017, and the album was released on 2 June 2017, by Columbia Records.
Opel is a 1988 album compiled from recordings made by former Pink Floyd frontman Syd Barrett between 1968 and 1970.
 The album is a compilation of unreleased material and alternate takes of recordings from sessions for Barrett's solo albums, "The Madcap Laughs" and "Barrett".
 Before they were vetoed by Pink Floyd, the album was to include two unreleased tracks that Barrett had worked on while with Pink Floyd, "Scream Thy Last Scream" and "Vegetable Man".
Ça Ira (French for "It'll be fine", subtitled "There is Hope") is the fourth studio album by Roger Waters.
 It is an opera in three acts and a concept album.
 The album is based on the French libretto co-written by Étienne and Nadine Roda-Gil on the historical subject of the early French Revolution. "
Ça Ira" was released 26 September 2005, as a double CD album featuring baritone Bryn Terfel, soprano Ying Huang, and tenor Paul Groves.
 The album received mixed reviews, with critics praising the composition but criticising its plot and simplicity.
The Final Cut is the twelfth studio album by the English progressive rock band Pink Floyd, released on 21 March 1983 by Harvest Records in the United Kingdom and on 2 April by Columbia Records in the United States.
 It was Pink Floyd's last studio album to include founding member, bass guitarist and songwriter Roger Waters, and their only album on which he alone is credited for writing and composition.
 It was also the only Pink Floyd album that does not feature keyboardist Richard Wright.
 Waters originally planned "The Final Cut" as a soundtrack album for the 1982 film "Pink Floyd – The Wall".
 With the onset of the Falklands War, he rewrote it as a concept album, exploring what he considered the betrayal of his father, who died serving in the Second World War.
 Waters sings most of the lyrics; lead guitarist David Gilmour provides lead vocals on only one track.
 The packaging, also designed by Waters, reflects the album's war theme.
"What God Wants, Part I" is the first song in a series of songs written and released by former Pink Floyd bassist, Roger Waters on his third solo album, "Amused to Death".
 "What God Wants" is separated into three parts, much like Pink Floyd's earlier work with "Another Brick in the Wall".
 Though the song is in three parts, "What God Wants Pt. 1", was the only one to be released as a single.
 The song features the guitar playing of Jeff Beck.
 This part in particular deals with the contradictory duality and hypocrisy perceived by Waters in dogmatic religion and its power over man.
 The following parts, along with the other songs on the album, deal with worship not only in religion but also in regard to materialism and consumption.
 All together, its viewpoint is on the power of simplistic conformity; how people adhere to something, not entirely by volition, but out of submission.