When Root arrived at the crease Australia had their hosts wobbling at 43-3 having opted to bat first.
Root was then dropped on nought by wicketkeeper Brad Haddin, a slice of luck he cashed in on to the tune of 134 runs as England ended the day on a promising 343-7.
Root’s fine form is fast becoming a given but he was aided this time by a brave 61 from county colleague Gary Ballance, who sustained several bruises as he battled both Mitchell Johnson and his own dip in form.
“Obviously, it wasn’t pretty at times, but it was vital that we got a decent partnership,” said Root of the stabilising 102-run stand.
“When you come into positions like that, after losing three wickets quite quickly, you’re going to get opportunities to score – because they’re going to have aggressive fields.
“It could have gone completely the other way – I could have got out second ball, then you look a little bit silly – but I had that fortune today, and could cash in and make the most of it.
“And Gary was so important for us – the mental strength he showed, determination and Yorkshire grit... the way he went about things was really pleasing to watch at the other end.
“That’s why he’s so integral to our team.”
When this match is filed away in the record books it is possible that Haddin’s one-handed spill could be seen as the decisive moment. If Root goes on to enjoy a prolific series it may be even more critical than that.
But the 24-year-old was mindful he could easily have been brooding over a duck, a price he feels would have been worth paying for committing to aggressive methods.
“There will be times when it doesn’t quite come off, and you look slightly stupid and play what looks like a horrendous shot and get out – but those are the sort of risks we’re taking by playing this attacking cricket,” he said.
“We want to continue to do that and really put sides under pressure whenever we can.
“It’s something we’ve been trying to work on since the start of the summer. It’s an approach we took against New Zealand, and it worked out really nicely.
“Fortunately, it was my day – I was the one who managed to do it – but everyone is going to take that approach.”
Australia seamer Josh Hazlewood, who returned figures of three for 70 on his Ashes debut to outshine the wicketless Mitchell Johnson, tipped his Baggy Green in Root’s direction.
He said: “The way he batted was pretty special. We’ll have to come back with a plan, or a couple of plans hopefully, to be able to nullify him over the rest of the series.
“He really waited for the bad ball throughout the whole innings. He’s a most improved player from last time we saw him and played against him.
“We’ll have to work a way to get him out.”
The 24-year-old, the baby among Michael Clarke’s ‘Dad’s Army’, pleaded ignorance when asked about fellow paceman Mitchell Starc’s finger-to-the-lips send-off of Ben Stokes - the first sight of sledging in the series.
“I’m not too sure what that was all about. He (Starc) had the last laugh this time, but we’ll see how it goes.”
Starc left the field in the closing stages of the day with a sore ankle.
He will be treated overnight but is not considered a serious injury concern.
James Faulkner put a difficult few days behind him to help Lancashire’s attempt to achieve what would be a remarkable victory in their County Championship game against Essex at Emirates Old Trafford.
The Australian all-rounder – charged last week with drink driving – made 68 in the home side’s formidable 402-8 declared and then took 3-28 as Essex collapsed to 81-5 before Nick Browne, who made a fine 78 not out, and James Foster, unbeaten on 13, guided their side to 139-5.