Opacic and Russell have put pen to paper to two-year deals, while Baptiste has signed a one-year deal for 2019.
Bowen has signed a one-year extension, which will see him enter his fourth NRL season with the club.
“Tom Opacic, Dan Russell and Javid Bowen give us much needed depth in the outside backs and complement the previous signings of Ben Barba and Nene Macdonald,” Cowboys Director of Football Peter Parr told the club’s website.
“We are delighted to secure the services of Kurt Baptiste as we believed we needed a genuine hooker to work in tandem with Jake Granville.
“Kurt’s form during his tenure at Canberra was excellent and I thought he was impressive this year for the Roosters in limited opportunities.”