Keary will first see out the year with the Roosters, who are well in the premiership picture with their current status sitting inside the top four.
Former NRL duo Jayden Nikorima and Siosiua Taukeiaho have been sacked from the Catalan Dragons overnight after a "highly unacceptable" incident.
The two players were terminated from their contracts with the club effective immediately after it was understood that they skipped out on attending a training session to attend a concert in the United Kingdom.
"Following a disciplinary process, the Catalans Dragons have decided to terminate the contracts of three of their Players with immediate effect," a club statement read.
"The players concerned are Siua Taukeiaho, Jayden Nikorima and Damel Diakhate.
"All Players were involved in an incident deemed to be highly unacceptable by the Club and contrary to the Club's values."
Debuting with the New Zealand Warriors in 2013, Taukeiaho moved to the Catalan Dragons after winning back-to-back premierships with the Sydney Roosters and was linked with a potential comeback to the NRL last season for the Bulldogs.
On the other hand, Jayden Nikorima - the brother of Dolphins playmaker Kodi Nikorima - moved to the club ahead of this season following stints with the Sydney Roosters and Melbourne Storm.
Their departures come after the Dragons have signed Canberra Raiders duo Nick Cotric and Elliott Whitehead for next season.
Luke Keary is also set to sign on with the club, and the official announcement will be made in the next couple of days.
A veteran of more than 200 NRL games with more than a decade of experience under his belt, Keary would become the third Australian veteran half to join the club in recent years after another pair of former Roosters, James Maloney and Mitchell Pearce, also elected to end their careers at the Dragons.
Keary will first see out the year with the Roosters, who are well in the premiership picture with their current status sitting inside the top four.