Kohli (131 runs off 96 balls) and Rohit (104 off 88) made merry on a batting beauty to guide India to 375 for five, the highest total posted by a visiting team in an ODI in Sri Lanka.
The final flourish was provided by comeback man Manish Pandey (50 n.O. Off 42) and MS Dhoni (49 n.O. Off 42), who achieved a memorable milestone of 300 ODIs.
Sri Lanka never looked like getting close to India's imposing total and could only manage 207 all out in 42.4 overs with Angelo Mathews' 70-run knock being the sole noteworthy batting performance.
India now lead the five-match series 4-0 and look set to complete another whitewash after blanking Sri Lanka in the preceding three Tests.
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Things are going from bad to worse for Sri Lanka, who needed to win at least two matches in the ongoing series to seal automatic qualification for the 2019 World Cup.
They can still directly qualify, provided the West Indies don't win more than three of their upcoming five ODIs against England.
India, opting to bat for the first time in the series, virtually batted the opposition out of the game.
Rohit, who hit back-to-back hundreds, now has 13 three- figure scores in the 50-over format.
Pandey too utilised his first chances of the series to the fullest while Dhoni missed out on his 100th ODI half century by a run.
The Dhoni-Pandey unbroken 101-run partnership for the sixth wicket yielded 101 runs in only 12.2 overs.
After winning the toss on a batting belter, skipper Kohli joined Rohit after Shikhar Dhawan (4) was dismissed trying to slash an Angelo Mathews delivery over point.
The first 50 came off 52 balls, but the innings slowly gathered pace as India crossed 100 off just 84 balls.
Kohli raced to his half-century off 38 balls even as their 50 partnership came off 46 balls.
The hectic pace of scoring continued as Kohli and Rohit celebrated their 100 partnership off only 76 balls with the latter also reaching half-century off 45 balls.
Kohli faced 96 balls and hit 17 fours as well as two sixes while Rohit's innings had 11 boundaries and three maximums.
Their partnership improved on the previous highest second wicket stand on Sri Lankan soil -- 197 runs added by Dhawan and Kohli in the first ODI of this current series in Dambulla.
It was also India's third-highest second wicket partnership against Sri Lanka in ODIs, after 318 at Taunton in May 1999, and 236 at Nagpur in March 1999 -- both set by Sourav Ganguly and Rahul Dravid.
This was also their third 200-plus stand as a pair equalling the record held jointly by Sachin Tendulkar and Ganguly, as well as Gautam Gambhir and Kohli.
Akila Dananjaya (1/68 in 10 overs) also did not cause any trouble to the batsmen.
India made three changes in the playing eleven --Pandey, Kuldeep Yadav (2/31) and Shardul Thakur (1/26), who finally made his international debut after getting a maiden call-up more than a year ago.