The man*, identified as "Paulie Tomas" on his Facebook page and aged in his 20s, was joined by at least a dozen friends on the corrugated iron rooftop of a Chippendale terrace house on Saturday afternoon.

They drank in the sunshine and posed for photos as the sun went down.

However at 2am, almost 12 hours after the festivities began, the man was found unconscious on the footpath of Myrtle Street.

Redfern police said he was injured as a result of "misadventure" but would not elaborate on how the group made it onto the third-storey roof or how he fell.

Miraculously, he survived the plunge and remained in a critical condition in Prince Alfred Hospital on Tuesday.

On Monday, he showed signs of improvement such as squeezing a hand and moving his toes but he has several fractures and possible brain injuries.

Friends who were celebrating with the man were overcome with shock and have rallied on social media.

"I've never met anyone more determined and stubborn than you are so im [sic] sure your recovery will be as miraculous and extraordinary as the rest of your life has been," a friend, Melissa Kavanagh, posted online.

"Hang in there Paulie, and fight with everything you have!" another friend, Jess Vertley, posted.

A police spokeswoman said there were no suspicious circumstances and police continue to investigate the incident.

It was one of four separate falls from roofs and balconies in NSW on Sunday.

A 20-year-old man died when he fell from the eighth-floor balcony of the Meriton building in Waterloo early on Sunday morning.

There were also accidental falls in Rozelle and The Entrance on the NSW central coast.

* An earlier version incorrectly said the man moved to Sydney from Brazil three years ago.