Roy, who scored 180 off just 151 balls, overhauled Alex Hales' 171 as the record highest individual ODI score for England.
Melbourne: Opener Jason Roy produced a superb performance with the bat as England thrashed Australia by five wickets, here at the Melbourne Cricket Ground (MCG) on Sunday to win the opening match of the Gillette ODI series. This is also England's first win of the tour after a dismal Ashes performance.
Roy, who scored 180 off just 151 balls, overhauled Alex Hales' 171 as the record highest individual ODI score for England. His thumping knock included 16 fours and five sixes.
Moreover, his 180 is also the highest score by a visiting batsman in Australia.
A 221 run stand between Roy and Joe Root (91*) also powered England to become the first team to chase down a 300+ score at the MCG.
Pat Cummins and Mitchell Starc picked up two wickets each.
Earlier, Australian opener Aaron Finch had scored his ninth one-day international century to leave England chasing a target of 305. The 31-year-old also became the equal-fourth fastest Australian to score 3,000 ODI runs.
Finch (107) along with Mitchell Marsh (50) and Marcus Stoinis (60) powered the hosts to 304-8.
Liam Plunkett picked up three wickets for England, while Adil Rashid scalped two.
The second ODI will be played on January 19 at The Gabba in Brisbane.