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.
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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.
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.