Van Rooyen's attempted spoil in a marking contest led to Gold Coast's Charlie Ballard being taken off the field on a stretcher on Saturday night.
The 20-year-old's action, in which his bicep ended up making contact with Ballard's head, was considered careless conduct, high contact and high impact.
Ballard was hurt but not concussed in the final-quarter incident and is expected to play against West Coast on Friday.
Adrian Anderson, representing van Rooyen, argued the action wasn't careless given it was a legitimate attempt to spoil.
Van Rooyen twice looked up at the ball on his way to making the spoil and he knocked back the suggestion from AFL counsel Andrew Woods he should have slowed up to protect his opponent.
"I don't think I would have been near the spoil if I had slowed up," van Rooyen said during his evidence.
"I didn't think I was going to make contact with Ballard's head. I was just trying to spoil the ball.
"I was just trying to go for the ball and I think I did a good job at that.
"I'm either touching the ball, or within millimetres of it. It wasn't my intention to hurt anyone."
Woods argued van Rooyen's decision to not look at the ball for the crucial final few metres led to the dangerous situation.
"There's nothing wrong with the intention to spoil," Woods said.
"But because of his speed and the position of his arm and where his eyes are mainly - not on the ball for the last five metres or so - it ends up being a blow to Ballard.
"The best thing he could do is guess where the ball would land based on Ballard's stance.
"If that's the case, it's careless."
The jury, led by tribunal chairman Jeff Gleeson, said the force of the blow was considerable and van Rooyen's actions were careless.
"We find that a reasonable player would have foreseen that in spoiling in the way he did, would almost inevitably have resulted in a forceful blow to Ballard's head," Gleeson said.
"He launched and extended his arm out and across Ballard's head. This was not permitted incidental contact."
Geelong forward Brad Close failed to overturn his one-match ban for a dangerous tackle and will miss Friday night's clash with Richmond at the MCG.
Close fronted the AFL Tribunal to contest the rough conduct charge for his pin-the-arms tackle that resulted in Adelaide's Jordan Dawson striking his head on the turf.
Dawson wasn't concussed in the incident.
Close's lawyer Ben Ihle argued it was Dawson's bid to break the tackle that forced both players to topple forward.
The jury upheld the original charge of careless conduct, medium impact and high contact.
"We accept that players tackle by grabbing an arm," Gleeson said.
"But if the tackler realises or should realise that the tackled player is coming to ground with momentum - and does not release the tackled player's arm that he might have used to protect himself - he is likely to have breached his duty of care to the player."
Carlton's Nic Newman will also front the Tribunal to contest his one-match ban for striking Brisbane's Lachie Neale with his elbow.
Port Adelaide forward Junior Rioli faces a lengthy suspension after being sent directly to the AFL Tribunal for striking Essendon's Jordan Ridley.
Rioli's case will be heard on Wednesday evening.Â