Buttler was promoted to open and continued his excellent form with another belligerent performance, smashing 61 in 30 balls with six 4s and five 6s after the home team had been put into bat on a balmy evening in Birmingham.
He and Roy (44) put Australia on the back foot from the start, compiling 95 for the first wicket from only 8.5 overs. Hales chipped in with 49 while Test captain Joe Root made 35 as England amassed 221-5, nine short of its highest T20 score.
Buttler's 21-ball half-century was the fastest by an England player in this format of cricket, surpassing Ravi Bopara's 23-ball effort against the same opponent in Hobart four years ago.
"We started outstandingly well. Jos and Jason really did get us off to a flyer, expressing themselves and making the most of that new ball and good wicket," captain Eoin Morgan said.
"Sometimes when you get off to a good start and you're 100 for none or one, you can fall short of getting 200, but we didn't take the foot off the pedal. We bat quite deep so we stuck to our mantra of going quite hard."
Australia, on the receiving end of a 5-0 defeat by England in this month's one-day internationals, made a valiant attempt to overhaul England's total thanks to captain Aaron Finch.
Opener Finch clubbed 84 in 41 balls with seven 4s and six 6s, but when he was caught just inside the long-on rope off Adil Rashid it left his teammates too much to do and his side was bowled out for 193. Leg-spinner Rashid took 3-27 and paceman Chris Jordan claimed 3-42.
Finch said he hoped Australia's inexperienced squad would take valuable lessons out of their winless one-day tour.
"It's been a really good learning curve for a lot of the young guys," he said. "We've had four months since the end of the season back home.
"For them to walk straight back in and perform against the best in the world, you can't come in 1 percent off the boil. They will learn a lot about their preparation going forward, that you have to hit the ground running and be 100 per cent committed and 100 per cent ready to go when you turn up and play that first game."