Morgan's choice was vindicated early on as Mark Wood, returning to the side after injury, removed the unsafe David Warner for two early on.
At the MCG yesterday, where he revealed his character and mental strength, Roy - who has yet to play a Test match - provided the sort of spark that was missing during the Ashes, riding his luck but carrying the fight to Australia's attack.
"It was our job to come in, lighten up the mood and bring more positivity and get the boys going really well", said Roy. "Giving them some of their own medicine was quite nice".
Moeen turned in a typically tidy 10-over spell, Liam Plunkett finished with three wickets and Adil Rashid bagged the prize scalp of Steve Smith for 23, but there was little doubting Mark Wood's starring role with the ball. The all-rounder also bowled tightly in his spell, taking 1-33 with the ball in hand.
It was left to some late-innings punch from Stoinis, who dominated an 85-run tandem with Tim Paine (27), to get them to an ultimately inferior 304.
The pair caned 47 off the first four overs and had racked up 53 off 28 balls before Bairstow was caught behind off Starc.
Here's the reaction to the Surrey star's record-breaking knock, starting with the man himself...
The success or otherwise of Morgan's team at next year's World Cup will be the ultimate judgment upon the tack taken by the European Central Bank in 2015, when they removed Peter Moores in favour of employing Bayliss with a clear mandate to improve England's limited overs cricket.
Alex Hales - 2/10 - Hales failed to capitalise on being dropped down the order as he could only muster 4 runs in his short innings. He chanced his arm and it came off and he was supported really well by Joe Root. Root rotated the strike superbly; supporting Roy on his way to 180.
Jos Buttler - 2/10 - Like Morgan, Buttler could not finish the innings as he made just 4 runs. "It is extremely special, especially after the Test series", he added. The nation's most successful Test off-spinner has only been an occasional choice in ODIs, playing the most recent of his 13 ODIs in August 2016. The second ODI will be played in Brisbane on 19th January.