Van Rooyen's bid to overturn or reduce his suspension at the AFL tribunal on Tuesday night fell flat, but the Demons have announced they will take the case to the AFL appeals board on Thursday night.
The Dees forward was charged with striking after he concussed Port Adelaide defender Aliir Aliir with a swinging arm during a marking contest on Saturday night at Adelaide Oval.
It was graded as severe impact, careless conduct and high impact.
After the 90-minute hearing on Tuesday, where van Rooyen testified that he was trying to mark the ball when he collected Aliir, the tribunal jury deliberated for nearly an hour before upholding the charge.
Melbourne had argued van Rooyen's attempt to mark the ball was not careless, but the tribunal rejected their case.
"The swing of van Rooyen's left arm constituted the act of a strike. It was a forceful blow. It was not simply a trailing or leading arm that Aliir collided with," AFL tribunal chairman Jeff Gleeson said in the verdict.
The fifth-placed Demons (15-7) face the ninth-placed Western Bulldogs at the MCG on Saturday before the finals begin.
It means if Melbourne fail to overturn or reduce van Rooyen's ban, they will need to win two finals games for him to be a chance of playing again this year.
The 23-year-old is having a breakout season, having kicked 42 goals in 22 games, including bags of six against St Kilda and Richmond.
