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Coleman says he will step down when his current contract expires at the end of the 2018 World Cup campaign.
He guided Wales to the Euro 2016 semi-finals in their first appearance at a major tournament in 58 years.
"Hopefully we'll be able to persuade him to stay on because what we've done over the past few years has been sensational," Roberts said.
"I haven't spoken to him about it yet. The plan is to get to Russia. I'm hoping there's 12 months until that decision has to be acted upon.
"During that time I'll certainly be talking to him about it. I know how much he's enjoyed the experience leading this group of players, leading the team behind the team, and leading the nation.
"He's obviously done a remarkable job. Anything's possible in football. Things change very quickly. Hopefully on this occasion Chris will change his mind."
Coleman's side drew 1-1 away to Serbia in their recent World Cup qualifier to remain unbeaten in their group.
Wales are currently four points behind Serbia and the Republic of Ireland in group D, with four matches remaining.
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Only the winners of the nine European World Cup qualifying groups will advance automatically to next year's finals in Russia, while the eight best runners-up enter the play-offs.
However, Roberts still believes finishing top is a realistic aim and is not ready to concede that Wales cannot win the group.
"All we can do is focus on the games coming up in September. Win those and see where it takes us," he said.
"But we know that we have to take maximum points really, and that's well within the reach of this group of players.
"The aim is to finish top of the group. If that doesn't happen we'll have to aim for the play-off spot. But we're prepared for either [scenario]."
After beating Moldova in their opening game in the group, Wales have drawn their last five matches.
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But Roberts says the coaching team have been happy with the performances.
"We've created more chances than the opposition in each of those games. So it's fine lines," he said.
"When we look at the games against Serbia - in the home game, they had one effort on target and they scored. And yet again last week they get one effort on target and they score.
"It's very difficult to stop a team for 90 minutes from getting one effort on target.
"Based on statistics, we've been really unlucky not to get maximum points out of most of the games, apart from [the 1-1 draw] with Georgia. That's the only game we didn't deserve maximum points.
"But we are where we are. We've got to continue to work hard. And we've got to continue to be effective in that final third, in particular in open play."
Wales assistant boss Osian Roberts hopes Chris Coleman can be persuaded to extend his stay as Wales manager.

The body was discovered by workmen at High Melton College on Tuesday.
South Yorkshire Police said formal identification had not taken place but confirmed officers had pulled the man's body from the tank on Wednesday.
Detectives are working with Yorkshire Water and underwater search teams to determine the circumstances surrounding what happened.
More stories from Sheffield and South Yorkshire
High Melton is a campus of Doncaster College.
A body discovered in a sewage tank at a Doncaster college is that of a man, police have said.

The Sun on Sunday has published a video showing the alleged incident, believed to have taken place on Sunday, 26 July.
"I wholeheartedly apologise for any offence I've caused," Vardy, 28, said.
"It was a regrettable error in judgement I take full responsibility for, and I accept my behaviour was not up to what's expected of me."
Vardy scored the opening goal in Leicester's 4-2 win against Sunderland on Saturday.
He has scored 26 goals in 98 league games for the Foxes and made his international debut for England in June.
A Leicester City spokesman added: "We expect the highest standards from our players on and off the pitch and for them to set an example as role models in our community.
"We have noted Jamie's apology and will begin a process of investigation into the incident imminently. There will be no further comment until this process has concluded."
Two months ago, Leicester sacked three players after they took part in a racist sex tape filmed on the club's end-of-season tour of Thailand.
Tom Hopper, Adam Smith and James Pearson - the son of former Foxes manager Nigel - had their contracts terminated following an internal investigation by the club.

Leicester's Jamie Vardy has apologised and his club have promised to carry out an investigation after claims that the striker made a racial slur in a casino.

