However, their aggressive strategy of giving themselves four overs to bowl at Australia before stumps proved fruitless as the tourists ended the day at 14-0.
Under the leadership of Ben Stokes and coach Brendon McCullum, known for their unconventional and attacking approach, England made a strong start with the bat in Birmingham.
But the crucial dismissals of Stokes and the fiery Harry Brook left the home side in a precarious position at 176-5, facing the imminent danger of a quick collapse.
However, as has been the case for many years, Root steadied the ship, putting together a partnership of 121 with fellow Yorkshireman Jonny Bairstow, who eventually fell for 78, to save his country in the hour of need again.
Root pulled out some outrageous shots in an incredible innings, with his century greeted with raucous applause by an Edgbaston crowd, with their former skipper raising home hopes of a first Ashes series win in eight years, finishing unbeaten on 118.
England did all they could to take a wicket before close of play, with Stuart Broad and Ollie Robinson steaming in from either end, but David Warner and Usman Khawaja stood firm.
Australia’s Nathan Lyon was taunted by sections of a capacity 25,000 crowd.
But he still took 4-149 as he moved to within nine wickets of 500 in Tests after bowling 29 overs — an unusually high number for an off-spinner on the first day of a Test.
England have won 11 of their last 13 Tests, with an aggressive approach, dubbed ‘Bazball’ in reference to coach Brendon McCullum’s nickname, exemplified by the aggressive run-scoring that was a hallmark of Bairstow’s innings.
They signalled their intentions from Friday’s first ball, with Zak Crawley driving Australia captain Pat Cummins through the covers for four in elegant fashion.
Recently crowned World Test champions Australia, however, hit back when Ben Duckett (12) was caught behind off recalled paceman Josh Hazlewood.
And Crawley fell for 61 off what became the last ball of the session, when paceman Scott Boland produced a superb delivery that leapt off a length and brushed the glove, with England 124-3 at lunch.
Harry Brook was out for 32 in bizarre fashion when he shouldered arms to Lyon, with the ball looping off the thigh pad and spinning into the stumps after Brook had lost sight of it.
Stokes then lasted just eight balls, caught behind on the drive off Hazlewood.
Australia thought they had the prized wicket of Root when he was given out lbw to Lyon, but the batsman’s immediate review confirmed he had gloved the ball.
(With Inputs from Agencies)