Khaled Salhah scored the only goal for an undermanned Curtin as Alex Grayson scored twice for Rockingham, with Ryan Kennedy, Max Snelson and David Clarke also scoring for the visitors.
It was Rockingham keeper Cyril Sharrock who was picking the ball out of the back of his net early on as Salhah rose tall to powerfully head home a Carlo Chiellini cross after four minutes.
Grayson then drew the sides level just minutes later as he poked home when Curtin thought they had a free kick in the middle of the park for a foul on Chiellini.
Ryan Kennedy then gave Rockingham the lead from a dead ball he put into the top corner.
The next 15 minutes were mayhem as Nicholl was sent from the pitch for a second bookable offence and Rockingham put two more away from set pieces, as Grayson scored his second and then Snelson got in on the action.
Rockingham had a 4-1 lead into the break, with Curtin facing a mountain of a task in the second half.
In the second half it was a case of what could have been for the home side, as Curtin peppered Sharrock�s goal but to no avail, as the Rockingham keeper was saved on more than one occasion by his defenders.
First it was Nathan Smith who had a chance for Curtin before Salhah saw his header cleared off the line and then Dilip Thapa was unlucky not to score after beating four players.
Clarke sealed the 5-1 win for Rockingham as Curtin committed bodies forward in the dying stages of the game.