The Airlie Birds took a commanding 36-10 lead into the half-time break.
Trialist Lee Smith and a second for Tuimavave help bring up 60 points.
Kieron Dixon managed two consolation tries for the Robins in the second half. The flyer scored his second with just three minutes left in the game.
But it’s a worring sign for Hull KR after they were thumped by Huddersfield last weekend.
Hull FC have secured back-to-back friendly victories after defeating Doncaster last weekend.