Trailing the visitors 0-1 in the five-match series, Miller stood out with his four for 43 effort while opening bowler captured three wickets as the Windies set themselves for series-levelling victory at the Providence stadium.
Even after losing openers Hamilton Masakadza and Vusi Sibanda inside seven overs, Zimbabwe appeared to put up a challenging total when Brendan Taylor (47) and wicketkeeper Tatenda Taibu (31) were involved in a 59-run partnership. But post their dismissal, the Zimbabweans, who pulled off a narrow two-run victory in the first one-dayer, lost the plot and eventually folded up for 206 with a ball to spare in their allotted 50 overs.
Elton Chigumbura hit an exact half-century for the visitors. But Chigumbura did not have much support from the other end as he struggled to regain the momentum that the Zimbabweans lost early in their innings.
Brendon Taylor and Tatenda Taibu had a nice little alliance but after the dismissal of the latter there was not much fight left in the Zimbabwe ranks.
The visitors, who scored a shock win in the first one-dayer, struggled against Roach and Miller.
Score Board
ZIMBABWE
H Masakadza c Miller b Roach 14
Sibanda (run out) 5
Taylor lbw Gayle 47
Taibu c Chanderpaul b Miller 31
Matsikenyeri c Gayle b Miller 2
Lamb c&b Miller 23
Chigumbura c D’narine b Roach 50
Cremer b Miller 17
Utseya (not out) 6
Price b Roach 0
Mpofu (run out) 0
Extras (B-1, LB-5, W-5) 11
Total (all out, 49.5 overs) 206
Fall of wickets: 1-6, 2-34, 3-93, 4-100, 5-107, 6-180, 7-183, 8-205, 9-206.
Bowling: Roach 9.5-0-37-3, Bernard 4-1-22-0, Benn 9-1-37-0, Sammy 5-0-17-0, Chris Gayle 10-0-25-1, Nikita Miller 9-0-43-4, Kieron Pollard 3-0-19-0.