Reports have also surfaced in Australia that Newcastle Knights have launched a bid to sign Wigan's England stand-off George Williams for next season.
Bateman, 24, will link up at the Raiders with his current Wigan team-mate Ryan Sutton as well as England internationals Elliott Whitehead, a close friend and former Bradford team-mate, and Josh Hodgson.
Canberra say they have been in negotiations with Bateman for several months but held back the announcement to give Wigan the chance to break the news, which they did on Wednesday.
Bateman has signed a three-year contract with the Raiders and has also agreed a three-year deal to return to Wigan as their marquee player from 2022.
Raiders recruitment and high-performance director Peter Mulholland said: "John is a wonderful talent who has the ability and skill set to play a number of positions.
"We've already seen the success of both Elliott Whitehead and Josh Hodgson transitioning from the Super League to the NRL and we see John as being a player who can make a similar impact in this competition.
"At 24, he's got the perfect mix of experience and youth and we're really looking forward to seeing him in green in 2019."
Meanwhile, the Titans say they have secured an agreement with Roberts to return to them next season on a two-year deal.
Roberts spent 2016-17 at the Gold Coast before moving to Warrington on a three-year deal at the end of last season.
Roberts, who kicked eight goals in the Wolves' 48-12 Challenge Cup semi-final win over Leeds on Sunday, opted to cut short his stay in Super League for family reasons.
Titans coach Garth Brennan said: "Tyrone is a very good half but will also add that real utility value to our squad and the fact he can play six, seven, nine or one makes him such a valuable commodity to have.
"He's played a number of representative matches and has been a seasoned NRL player for well over five years, so he knows what it takes to compete at the top.
"Tyrone's been part of a successful club overseas who just qualified for the Challenge Cup final at Wembley so the experience he has gained in his short time over in England will be extremely valuable to bring back to our young squad.
"He has many friends still at the club and I know he'll settle back in without any issues."
Warrington have already announced the signing of Canberra half-back Blake Austin as their replacement marquee player for 2019.
