The Demons extended their perfect MCG record this year to 9-0, after being given some trouble by Richmond in the first term before coasting to a 16.15 (111) to 9.11 (65) win in front of 32,893 fans.
Sunday's result consolidates Melbourne's position in the AFL's top six, with the Demons virtually guaranteed to feature in at least the wildcard round in Steven King's first season as coach.
After a starring five-goal effort in Melbourne's surprise demolition of Hawthorn last week, van Rooyen took that confidence into a date with the rebuilding Tigers.
He became the first Demons player to have back-to-back five-goal hauls since now-GWS forward Jesse Hogan in 2018.
After kicking just two goals in a lean four-week patch, van Rooyen has notched 14 in his past three appearances.
The 23-year-old's efforts took him to 35 goals this season - his best return in a single campaign since debuting in 2023.
"Rooey's just a young key forward, and for the games he's played and what he's produced, I think we get a bit impatient for the young keys to produce straight away," King said.
"Sometimes you can fall in the trap of putting too much pressure on yourself and thinking about outcomes, rather than the process.
"I feel like Rooey's matured enough now to realise if he works hard and competes strongly, the craft, the talent, that comes out.
"He's just doing that more regularly."
Melbourne colossus Max Gawn put in a typically masterful shift in the ruck, and pushed forward to slot two goals.
His opposing captain and ruckman Toby Nankervis also kicked two goals for Richmond, but Gawn easily won the battle around the ground and in the middle.
Superstar Kysaiah Pickett was serviceable without being game-changing, but still provided arguably the game's highlight - a mark-of-the-year contender after standing on top of Nankervis in the second quarter.
Veteran Jake Melksham played an important role up forward with two goals after being a late inclusion for Harrison Petty (hamstring).
Richmond, who slumped to 2-15 and 10-54 in the Adem Yze era, had a few reasons to celebrate, including when their eighth debutant of the season, Zane Peucker, slotted a goal with his first kick in the AFL and was mobbed by teammates.
Richmond coach Adem Yze pushed back when asked if the club was becoming too accepting of defeats.
"I reckon if you sat in my team meeting after the game, you would have sensed some disappointment within our team," he said.
"I don't need to shy away from the fact that we lost the game today, and we're not happy - I tried to say that at the start.
"We weren't good enough in the second quarter and we got taught a footy lesson."
Before the match, both teams paid tribute to community footballer Nathan Fitzgerald, who tragically died following an on-field incident this month.
Fitzgerald, who played for the Epping Football Netball Club, was a diehard Richmond supporter and his brother Matt tossed the coin before Sunday's match.
