The Panthers were then forced to repel a sustained spell of Roosters pressure.
The hosts did everything but cross the line as Cleary's well organised defence held them out, with two Mitchell Pearce bombs only just evading the hands of winger Justin Carney and Anthony Minichiello coughing the ball up just short of the line.
The Panthers then doubled their advantage with Jennings' first try of the afternoon five minutes before halftime.
Hardworking backrower Nathan Smith started the move by breaking a tackle on the right-hand and spreading the ball wide where Luke Walsh ran the ball well, then found Jennings, who stepped from left to right and eased his way to the line.
The Roosters continued to toil after the break, with Pearce's probings failing to produce any real quality.
Jennings all but secured the two points on the hour-mark, when Sam Perrett and Boyd Cordner managed to lose possession between them and the Test star pounced on the loose ball to sprint 40 metres along the sideline to score.
Walsh, who looked the more composed of the two halfbacks on show, kicked three goals to add some gloss to the win.
-AAP