Young full-back Michael Le Bourgeois scored 19 of his side's points as Jersey won 24-9 at Rosslyn Park.
Le Bourgeois touched down in the second half, converting his own try and was also successful with four penalties.
The island side's captain Paul Rodgers scored in the final minute to seal Jersey's third win of the National League One season.
Rosslyn Park's points came from the boots of Will Robinson and Ed Lewis-Pratt (2).
"We stuck to our patterns and we managed to eventually start playing in the right areas," Le Bourgeois told BBC Radio Jersey.
"We forced them to make mistakes and we managed to capitalise on those mistakes.
"I was just trying to play my own game really and be more of a leader, trying to keep the other players upbeat and keep the morale pretty high."
Jersey climb to sixth spot in the table while Rosslyn Park drop a place to 11th.