Under new anti-terror measures, a 2.6-metre barrier could soon block public access to the much-loved grassy space.
The mass tumble took place on Saturday morning, after news of the event spread on Facebook.
Lester Yao, who organised it, said he felt the architect had wanted the public to enjoy the grounds freely.
While he had originally planned the roll as a gathering of family and friends, he was delighted when almost 3,000 people expressed interest in the unique protest via Facebook.
Cricket fans treated to spectacular Canberra sunset
Pro-asylum protest halts Australia's parliament
Syrian refugee gets top results in Oz
Explaining the event, he wrote: "It's a story I hear often from people that live in Canberra or visit Canberra and the Parliament House. They walk up that beautiful green lawn and see the amazing view of Canberra, then they fall to their knees and roll down the hill.
"This simple fun action embodies a very simple yet powerful symbol of democracy. That the citizens can walk up and over their elected government.
"At least that's what I believe the architect behind the design of the Parliament House intended."
Mr Yao, 34, lives in Canberra but is originally from the Philippines. The Canberra Times reported that he recently took a visiting cousin for a joyful tumble down the Parliament House hill - which got the ball rolling on his protest.
No firm timetable has been given for the controversial fence, which is part of a A$60m (Â£35m; $44m) security blitz at the seat of Australia's government, but work could begin by summer 2017.
Prime Minister Malcolm Turnbull has defended the costly plans, telling The Huffington Post Australia that "parliament is the people's house," but that "getting that balance right" on security is "critically important".
MPs recently voted in favour of the fence - but not all of them support it.
MP Andrew Broad of the National Party of Australia told News.com.au children should be able to roll down the iconic grass.
"Let's not let terrorists destroy our way of life," he urged.
Mr Broad said that while he has not indulged in a hill roll since he was a child, Australia's leaders should consider taking part.
"I reckon at the end of the year that'd be a good look; all the pollies [politicians] finish the parliament with a good roll down the grass and tell people that parliament ultimately is about a bit of fun," he said.

Ray Jennings, a former South Africa international wicketkeeper, only saw his son had made a ton against India when his power returned an hour later.
"When he reached 96 the electricity went off, so I missed his hundred," he told BBC Radio Newcastle.
"When it went back on an hour later, I watched one ball and then he got out."
Durham left-hander Keaton, whose mother was born in Sunderland, became eligible to play for England in 2016 after serving a four-year qualification period.
The 24-year-old opener top-scored with 112 as England ended day one on 288-5 in the fourth Test against India.
Media playback is not supported on this device
Asked what he said when the power went off, Jennings Snr said: "I'm sure a lot of your listeners would know it wouldn't have been a long sentence - it would've been short and abrupt, but I wouldn't be able to repeat it on air.
"It was a little bit of a bitter ending, but I'm very happy to know he actually ended up getting a hundred.
"Keaton keeps on telling me that one of the things I've done well is marry a British lady, so she's [his mum] over the moon and Keaton's over the moon.
"I've suddenly moved away from supporting a South African side to supporting an English side, and I'm very proud to actually say that.
"It's probably the most enjoyable sporting day I've ever had - for someone in your own family to achieve something like that has really been a blessing for me."
Hundreds of Australians have gathered to roll on the lawns of Parliament House in Canberra, in protest against plans to build a security fence there.
[NEXT_CONCEPT]
Keaton Jennings' dad Ray says he missed his son's England debut century because of a power cut while he was watching the Test on television in Mauritius.