Root raised three places after his innings of 122, slotting in at number five on the rankings for batsmen, edging ahead of New Zealand's Henry Nicholls, who has the same rating points.
Jos Buttler, who backed up Root with a pair of half-centuries in the third Test, and Ben Stokes, who top-scored in the first innings, rose by eight places to number 26 and seven spots to number 34 respectively.
West Indies' Jason Holder remains at number 36, while Roston Chase, who made a fighting century, climbed 10 places to be number 41, while taking the 13th place among allrounders.
Stokes, who took two wickets in the St Lucia Test, made a small gain to be number four on the rankings for allrounders, a chart led by Holder.
Among the bowlers, Mark Wood, who bowled a fiery spell for a maiden five-wicket haul in West Indies' first innings, was the big gainer, vaulting 12 places to number 52. Kemar Roach (11) and Alzarri Joseph (51) for West Indies, and Moeen Ali (27) for England made slight gains.