|Fourth one-day international, Kia Oval|
|Sri Lanka 305-5 (42 overs): Mendis 77, Mathews 67*, Chandimal 63*, Gunathilaka 62|
|England 309-4 (40.1 overs), revised target 308: Roy 162, Root 65|
|England won by six wickets (DLS)|
Jason Roy scored a second century in three games to give England a series-clinching six-wicket win over Sri Lanka in the fourth one-day international.
Roy made 162, the second-highest score by an England batsman in an ODI.
It led England to 308, their second-highest successful ODI chase, with 11 balls to spare in a match reduced to 42 overs because of rain at The Oval.
Sri Lanka posted 305-5, a total increased by the DLS method, but could not stop England taking a 2-0 lead.
It is a third one-day series win in five since the awful World Cup campaign of 2015. The two defeats, against Australia and South Africa, were both in deciding rubbers.
Sri Lanka are still searching for their first win over England on this tour, with only Saturday's fifth ODI at Cardiff and a Twenty20 in Southampton on Tuesday remaining.
Roy epitomises England revolution
Opener Roy, brought into the England side immediately after the World Cup, has epitomised the improvement which has seen them score one-day runs faster than any other international team since the tournament in Australia and New Zealand.
Following his record-breaking stand of 256 with Alex Hales to win the second ODI, the Surrey right-hander could not be contained on a perfect batting surface at his home ground.
With a bottom-hand technique that saw him take 120 of his runs on the leg side, Roy three times shimmied down the pitch to hit sixes over long-on.
After Moeen Ali, opening because Hales had a stiff back, edged behind, Roy shared 149 with Joe Root, who cut and pulled his way to a much-needed 65.
Dropped by bowler Suranga Lakmal on 133, Roy seemed certain to better the 167 not out made by Robin Smith against Australia in 1993 when he missed a swipe at a Nuwan Pradeep slower ball and was bowled.
That left Jonny Bairstow and Jos Buttler to complete England's fifth successful chase in excess of 300 and their third in the past year. A feat once remarkable for this team is now becoming routine.
Sri Lanka improve - but not enough
Asked to have first use of such a true surface, Sri Lanka put in their best batting effort of the series but, despite four men passing 60, lacked a match-winning contribution.
Kusal Mendis added drives to his usual strong back-foot play in 77, while Danushka Gunathilaka drove well and worked to the leg side effectively in making 62.
They shared 128 for the second wicket but both fell after the rain, which arrived in the 19th over, to the leg-spin of Adil Rashid, who was without the accuracy he displayed earlier in the series.
Despite the platform that has been previously lacking, Sri Lanka were never able to fully kick-on, even though Dinesh Chandimal took sixes over mid-wicket and third man in his 63.
After he was bowled by David Willey, it was left to Angelo Mathews to provide the late impetus with an unbeaten 67.
Eighty-eight runs came in the final nine overs and the adjusted total looked at least competitive. Roy proved it was anything but.
'I'll never forget that' - what they said
Man of the match Jason Roy on BBC Test Match Special: "To contribute in a big way like that is extremely special. I'll never forget that.
"A lot of hard work has been put in and we reap the rewards. These are very exciting times for English cricket."
England captain Eoin Morgan: "Jason Roy is making the most of his form. That is a big thing in international cricket - you cash in and he is certainly doing that.
"It is nice for him to be second in the list. He has played a magnificent innings."
Sri Lanka captain Angelo Mathews: "I thought we had a good score on the board. Our bowlers were pretty ordinary and Jason took the game away from us."
The stats you may have missed
- With scores of 112*, 5* and 162*, Jason Roy made 279 runs between dismissals in this series. He is averaging 141
- Roy is the fifth England opener to score two centuries in a bilateral series, after Graham Gooch, Nick Knight, Kevin Pietersen and Alastair Cook
- Roy and Joe Root's partnership of 149 is the highest second-wicket stand for England against Sri Lanka in ODIs, beating Alec Stewart and Graeme Hick's 125 in the 1999 World Cup
- England are scoring at around 100 runs per 100 balls since the World Cup in 2015; before that they were scoring at 83 per 100 balls
|The series so far|
|1st ODI, Trent Bridge: Match tied|
|2nd ODI, Edgbaston: England won by 10 wickets|
|3rd ODI, Bristol: Match abandoned|
|4th ODI, The Oval: England won by six wickets|
|5th ODI, Cardiff: 2 July, 10:30 BST|
|Full tour schedule|