The 24-year-old Paterson, who has a British passport, played under Rovers coach Craig Sandercock for Newcastle Knights before joining the Cowboys midway through last season.
"Cory is a great acquisition," said Sandercock.
"He is a young player who has already achieved a lot in the game at a young age. He brings all the qualities on and off the field that we are looking for.
"Cory is coming to Rovers for the right reasons and I am really excited to be able to work with him again."
The 6ft 5in, 16st Paterson represented Australia at schoolboy level in 2005 and has also been a member of the Indigenous team in the annual All Stars match for the last three seasons.
He said: "I'm really excited about my move to Hull KR. I've been following the club for a while since Sandy and a couple of my old team-mates, Con Mika and Shannon McDonnell, went there.
"I'm lucky I've got a British passport and playing in the Super League was always something I wanted to do so when the chance came up to play for Hull Kingston Rovers, I couldn't resist.
"The timing is right for me and my young family to make the move. We're all keen to get over there and experience a different lifestyle and culture and for me to play some good footy."
Paterson will join up with his team-mates ahead of pre-season training in November subject to receiving a visa and work permit.