Root has been promoted one place up the order following former number three Nick Compton's decision to take time out from cricket following a poor series against Sri Lanka.
Although not true of Compton, number three has historically been the place occupied by a team's leading batsman.
Root, who had a brief spell as an England opener, was persuaded to make the move by captain Alastair Cook and coach Trevor Bayliss.
Now the 25-year-old Yorkshireman will slot in at number three for the first of a four-Test series against Pakistan starting at Lord's on Thursday.
"We had a few discussions throughout the season that it could be a possibility moving forward," Root told a Lord's news conference on Tuesday.
"I think the fact I had quite a long time to think about it and to chat it over with the selectors and Trevor and Cooky, it probably made it a bit easier, rather than being thrown into the role," added Root, who has scored nearly 3,500 runs in his 42 Tests at an average of over 52 with nine hundreds.
"The way they've dealt with it has been really good and it's given me time to get my head around it.
"I feel pretty comfortable going into the series and it's now just about trying to make sure that moving forward that's something I feel comfortable with and I can keep making big scores and contributing to winning Test matches."
Root denied England's middle-order would be weakened by his promotion and the ongoing absence through injury of all-rounder Ben Stokes.
"I think that's probably harsh," said Root.
"Someone like Jonny Bairstow would consider himself a middle-order batsman and he's taken his game to another level."
He added: "Guys like James Vince, who will really be looking forward to getting back out playing red-ball cricket again.
"He's got a little bit of experience under his belt and will gain confidence from that."
Pakistan left-arm quick Mohammad Amir is set to make his return to Test cricket on Thursday at Lord's -- the ground where he incurred a five-year ban for deliberately bowling no-balls against England in the 2010 "spot-fixing" row.