The Demons started Saturday night in seventh spot, but they're now just outside the top four on percentage after recording a thumping 20.12 (132) to 8.8 (56) victory at Adelaide Oval.
The big talking point was the van Rooyen incident, with the Demons spearhead set to face MRO scrutiny with the finals just a few weeks away.
The Melbourne forward was attempting to spoil an Aliir mark in the second term, but appeared to mistime it and he struck the Power defender high with a swinging arm.
Alilir, who went down and had to be helped off the field by trainers, failed his HIA test and spent the rest of his milestone game watching from the bench.
"He's okay," Power coach Josh Carr said of Aliir post-game.
"Obviously, he's a little bit flat and a bit quiet, but Aliir is a leader. He'll find a way to get himself up.
"Look, this is honest truth. I haven't looked at it closely, but my first thought of it is I can see how it happens.
"It obviously didn't look great, but I didn't think it was overly malice either."
Demons coach Steven King, who said he'd 'hadn't really seen' the incident, added it was "really unfortunate" for the Power intercept defender.Â
Skipper Max Gawn dominated with 25 disposals and 22 hit-outs, while Bayley Fritsch and Kade Chandler kicked four goals apiece for the Demons.
For Port Adelaide, Brownlow Medallist Ollie Wines had 31 possessions and Mitch Georgiades booted four majors.
The Power had four of the first five clearances of the game, but it was all Melbourne right from the outset.
Four consecutive goals to start the game - from van Rooyen, Tom Sparrow, Bailey Laurie and Chandler in his 100th game - made for a very quiet Adelaide Oval.
Georgiades soon had Port Adelaide's first goal, but three consecutive Melbourne goals - including a sharp dribbling snap goal by Chandler - saw the Demons leading by 36 points at the first change.
A bake by Power coach Josh Carr at quarter-time had the desired response, with his side booting the first two goals of the second term.
A highlight for Power fans was a huge leap by Georgiades, who narrowly spilled what would likely have been the mark of the year had it stuck.
Port supporters had little else to cheer about as the Demons maintained a six-goal buffer at the main break.
Melbourne piled on the goals in the second half, leading by 53 points at the last change and kicking a further five goals in the final term.
