Skipper Michael Dobson has exercised an opt-out clause in his contract to secure a return to the NRL from 2014 while city rivals Hull FC have confirmed the signing of prop Mickey Paea.
Rovers are also resigned to losing influential Australian forward Cory Paterson, who has asked for a release on compassionate grounds.
The club have yet to comment on Dobson's departure but chairman Neil Hudgell revealed the opt-out clause earlier this week and on Friday, Newcastle Knights announced his capture on a 12-month contract.
"We look forward to Michael joining our club for the 2014 season," Knights chief executive Matt Gidley said. "Michael has been one of the best half-backs in the Super League for a number of years now and will bring further depth in our half-back ranks behind Jarrod Mullen and Tyrone Roberts."
The 27-year-old Dobson has so far scored 51 tries and kicked 475 goals in 134 appearances for the Robins and was named in the Super League Dream Team for 2009 and 2010.
The formern Australian schoolboy international also made 20 appearances for Canberra and had spells in Super League with Catalan Dragons and Wigan. Hudgell revealed earlier this week that he had rejected a "big-money" offer for Dobson from big-spending Salford.
Meanwhile, Paea, 27, has agreed a two-year contract with Hull after rejecting the offer of a new deal with the Robins and abandoning plans to return to the NRL.
"I have enjoyed my time in England and I'm settled in Hull so that made a tough decision a little easier but it has been difficult with a number of options on the table," Paea said. "I have been grateful for the opportunity at Hull KR but I felt after two years with the club I needed a fresh start and, after weighing up my options, Hull FC was the best fit for me and my wife.
"I have a lot of respect for Hull KR and their supporters and I will give my all to the club for the remainder of the year and look forward to joining up with Hull FC in the close season."