The 24-year-old Yorkshireman was unbeaten on 118 at the close of play while Jos Buttler ended on four not out on a good wicket for batting.
Earlier, England captain Alastair Cook produced a welcome return to form with 76 while Gary Ballance hit 77 and Jonathan Trott chipped in with 59.
Cook was bowled by Shannon Gabriel when he dragged a bottom edge on to the stumps, leaving the left-hander still searching for his first test century in almost two years.
Gabriel, playing in this match in place of the injured Jerome Taylor, then forced Ian Bell (one) to play the ball on to his stumps following an ill-judged attempt to cut.
The two strikes offered encouragement to a West Indies attack that bowled with discipline.
Cook's 125-run opening partnership with Trott had laid the foundations for England.
Trott was dismissed when he edged a full ball from leg-spinner Devendra Bishoo to Jermaine Blackwood at second slip.
It was England's first century opening stand since March 2013.
Root and Ballance then combined for 165 for the fourth wicket before the latter played a floated delivery from off-spinner Marlon Samuels on to his stumps.
Moeen Ali narrowly escaped a run-out attempt but did not last much longer, run out for a duck by a throw from Blackwood.
Ben Stokes then fell for eight as he spooned a catch to Blackwood at deep mid-wicket to give Bishoo his second wicket of the innings.
There has been no love lost between Stokes and Samuels throughout the series and the West Indian stood to attention and gave an army salute to the England all-rounder as he walked off the field.
The first test of the three-match series was drawn.
Original source: Rampant Root puts England in charge