"You get three players with Ben and, on his day, probably the best three players within the side all in one," Root said.
"It is a huge boost to have him coming back. He is such a good character around the dressing-room. When he speaks about the game, he gets everyone's attention and people listen."
Stokes has played two tests against New Zealand, both in May 2015.
The first – his 10th cap in a 39-test career – is unlikely to have been forgotten by six incumbent Black Caps at Lord's.
England had been reduced to 30 for four on the first morning after getting sent in. The mercury in the 'Bring Back Kevin Pietersen' thermometer threatened to burst.
Then Stokes and Root put on 161 for the fifth wicket to draw them back into the game. Stokes made 92 off 94 balls.
"I always back the way I play, regardless of the situation," he said at the time.
"Another day I could have looked like a wally and nicked out for 20. Farby [temporary now assistant coach Paul Farbrace] said 'everyone backs you in the changing room. Don't change anything because of the three lions' [the symbol on England's crest]."
Stokes doubled down with 101 off 92 balls in the second innings on what became a man-of-the-match performance combined with three second innings wickets for 38.
The plan seemed to be to pitch short because Stokes would be tempted to hook and pull in the air. He took the bait and triumphed. Little appears to have changed in his cricketing disposition since.
What has evolved after that match is day-night test cricket, which debuted in November 2015 between New Zealand and Australia at Adelaide.
The pink ball used had four strips of green seam and two of white. It is now stitched in black.
New Zealand captain Kane Williamson appreciated the change.
"Over the last 10 days [of practice] it's easier to identify the seam.
"I recall with the last one where you couldn't see the seam and sometimes it was hard to get your bearings of where it was square of the wicket, maybe if there was a big slash.
"The lights would shine on the fluorescent pink and make it a bit different to see."
Root said that regardless of the pink ball under lights, cricketing fundamentals could not be forgotten.
"We're still trying to work out if it makes a huge difference. Ultimately the basics are there, and proven to work across three formats."