With Stokes left out of the squad for the Oval clash after breaking a midnight curfew along with teammate Gus Atkinson, Root agreed to captain England for the first time since 2022.
Stokes and Atkinson became embroiled in an incident at a London nightclub while celebrating England's first Test win against New Zealand, prompting reports that the Durham all-rounder could be stripped of the captaincy or retire from international cricket.
Root led England in a record 64 matches before being replaced by Stokes once the leadership role took a heavy toll on his form and peace of mind.
England won just one of their last 17 Tests prior to Root stepping down as captain.
The 35-year-old batsman believes he is in a "different place" now, making him confident he will be able to lift the mood around the England squad after a turbulent period.
"I never thought I'd be sat here talking to you guys as England captain again. Zero chance... 0.1 per cent," he told reporters on Tuesday.
"The only thinking that came to my mind is what is the best thing for this team, is it going to have a big effect on me and my personal life and which outweighed the other.
"The fact is, it felt like it was the right thing to take this on, so I tried to make it as simple as that. I think I am in a very different place to when I finished.
"To be captaining this group of players is a really exciting opportunity. It's a game-by-game basis, I think. Let's not look beyond this week."
England head coach Brendon McCullum refused to be drawn on Stokes' status ahead of Wednesday's opening day of the second Test.
Amid an England and Wales Cricket Board investigation into the late-night incident, McCullum on Monday said he was concerned about Stokes' well-being.
Root, who is a close friend of the all-rounder, could lead England again in the third Test at Trent Bridge, which begins just three days after the scheduled finish at the Oval.
"I've spoken to him a number of times over the last week or so," Root said of Stokes. "We're close friends, and I think they should stay as privileged conversations between me and him.
"When it comes to how Ben's feeling, how he is, I think they're all questions that he should be answering himself. I'm sure, at the right time and when he's ready, he will."
Asked if Stokes could command the same authority after flouting a curfew he helped bring in, Root added: "I'm sure he has this respect of everyone in our dressing room. He's been a phenomenal leader for the last four years, and the way he's captained has been brilliant.
"He's a talismanic player and a great friend to a number of the guys, so of course there's a huge amount of respect there from everyone."
