Rosenfeld grew up in the Melbourne suburb of Malvern, where he dreamed of being a doctor from the age of five, and he tended to the family pets wearing a borrowed lab coat.

He obtained a PhD from the University of Connecticut in 1983, with his dissertation "Neuronal and glial abnormalities in myelin deficient mutant mice".

[3] Rosenfeld joined the Army Reserve in 1984 and his ongoing interest in Third World medicine started with a six-month posting to Papua New Guinea.

[7][8] He continued to make regular tours to disadvantaged countries and his unit was sent to war-ravaged Rwanda in 1995 as part of a UN mission; he was a general surgeon with the rank of lieutenant-colonel.

[7][3] By 2011 he was a brigadier, still returning to Papua New Guinea each year to train local medical staff in advanced surgical techniques.

He served on eight deployments, including to Rwanda, East Timor, Bougainville, Solomon Islands and Iraq, and by 2018 he had risen to the rank of major general in the Australian Defence Force.

[11][12][13] As of November 2021[update], he is Senior Neurosurgeon in the Department of Neurosurgery at The Alfred Hospital,[2] and the Emeritus Professor of Surgery at Monash University.

[15] In 2001, he won international acclaim for performing life-changing surgery to remove a hypothalamic hamartoma from a nine-year-old British boy, Sebastian Selo.

The technique had previously been used successfully on 18 children at that time, but Selo was the most critical; since he was a baby he suffered up to 100 epileptic fits each day and difficulty speaking, caused by a tumour the size of a grape which had grown in his brain, about 10 centimetres (4 in) down, behind his eyes.

[20][21] In 2011, he published in The New England Journal of Medicine the first multicentre randomised controlled trial about the effectiveness of decompressive craniectomy (surgically removing a section of skull to allow the pressure from swelling to abate), compared to drug therapy.

[22][23] His team has developed an artificial vision system named Gennaris that may provide a degree of sight for blind people.

[24] It uses special glasses that connect wirelessly to an implant on the surface of the brain, generating a matrix of 172 spots called "phosphenes" (to expand to 473) to allow that the person to perceive a rudimentary view of whatever is there.

In 2008, together with psychiatrist Major Nick Ford, he warned about unidentified brain injuries which returned military suffer, caused by pressure waves from explosions.

[40][41] In June 2013, he was appointed an Officer of the Order of the British Empire (OBE),[42] presented in person by Queen Elizabeth II and the Governor-General of Papua New Guinea.