Coming in the wake of half-centuries in the drawn first Test in Antigua, the 24-year-old Yorkshireman's unbeaten 118 extended his excellent run of form and ensured the tourists made good use of the first sun-drenched day of the match.
They will go into the penultimate day ahead by 74 runs with Root and Jos Buttler seeking to build on that advantage in the quest for the victory on the last day that escaped them last week at the Sir Vivian Richards Stadium.
"We've got plenty of batting left in that dressing room and we'll want to get a big lead and only bat once."
Root's commanding knock, his first Test century outside of England, came off 125 deliveries and was embellished by 13 fours and two sixes.
More From This Section
He dominated a 165-run fourth-wicket partnership with Gary Ballance and almost knocked the fight out of the West Indies after fast bowler Shannon Gabriel made two important strikes in the early afternoon to give his team hope.
He dragged a wide delivery from part-time spinner Marlon Samuels onto the stumps and then watched from the pavilion as new batsman Moeen Ali ran himself out without scoring.
Ben Stokes didn't last long, hoisting a Devendra Bishoo long-hop to Jermaine Blackwood on the midwicket boundary to take some of the gloss off England's effort as they lost three wickets for 35 runs near the end of a day.