As well as Hopoate and Matai, Jamie Lyon, Daly Cherry-Evans, Glenn Stewart and Tony Williams scored tries for the Sea Eagles, while Lyon had an off day with the boot with two from eight.
For the Roosters, Aidan Guerra and Phil Graham scored four-pointers, while Todd Carney missed with two conversion attempts.
The Sea Eagles led 12-0 after three first-half tries and extended that by four just five minutes after the break when Glenn Stewart picked up the ball from the back of a scrum 10m out and dummied his way to the line.
It was 22-0 four minutes later when wrecking ball Williams ran over Mitchell Pearce and Lyon finally nailed a conversion.
It started getting embarrassing for the Roosters when Kieran Foran was ruled to have performed a one-on-one strip on Jason Ryles and the five-eighth sent centre Matai over.
The Roosters got one back through Guerra in the 63rd before Hopoate's second four minutes later from a superb Brett Stewart offload.
Matai's second, when he slammed the ball down despite being held by several Roosters defenders, made it 36-4 before the Roosters scored the try of the match, Graham completing an amazing length of the field effort in the final minute.
MANLY 36 (W Hopoate 2 S Matai 2 D Cherry-Evans J Lyon G Stewart T Williams tries J Lyon 2 goals) bt SYDNEY ROOSTERS 8 (P Graham A Guerra tries) at Brookvale Oval. Referee: Matt Cecchin, Tony De Las Heras. Crowd: 13,743.
- AAP