Hales came in and immediately got to work, putting on another 151 runs with Bairstow, who holed out in the deep to the off spin of Ashton Agar for 139.
Captain Eoin Morgan (67) also put in his late challenge for the headlines by hitting England's fastest ever 50, from just 21 balls, in the third century stand of the innings, before he and Hales (147) holed out to successive deliveries from Jhye Richardson.
England have never clean swept Australia in a series of more than three matches before, but the signs of that duck being broken looked ominous in Nottingham on Tuesday as Eoin Morgan's side crushed the world champions by 242 runs. England opening pair of Alex Hales and Jonny Bairstow added 159 runs together before Roy was dismissed for 82.
334 - Australia's highest successful run-chase, prior to this match. Surrey had hammered the gargantuan total against Gloucestershire at The Oval during the 2007 Friends Provident Trophy.
It was a remarkable day of shot-making by England's batsmen though as they carved an ODI record 62 boundaries, including 21 sixes. The 31-year old now scored a record 5443 runs for England in his 6187 ODI runs. Bairstow reached his sixth hundred in 69 balls.
Australia skipper Tim Paine elected to bowl first and was soon regretting that decision as the home batsmen ran riot against his inexperienced attack. In a series of social media posts, Ganguly wrote, "To see nearly 500 runs scored in 50 overs in England is scaring me, bout the health of the game and where it's going".
Having recovered from the back spasm that kept him out of the Cardiff match, Morgan not only recorded the quickest fifty in England's ODI history but passed Ian Bell's record to become England's most prolific ODI run-scorer in the process.
Australia, however, were gifted a wicket when Roy ran himself out going for a needless second run. And after Short chipped one to mid-on, Head poked a return catch to Moeen Ali and Shaun Marsh lofted to long-on. The top three are a huge asset to have. Suffice to say, all pretence of maintaining a balance between bat and ball disappears in such circumstances.