He arrived in Western Australia in 1895 and settled in Fremantle, where he initially worked as a produce merchant before joining the public service.
He became the assistant storekeeper at Fremantle Prison in 1910.
Rocke entered parliament at the 1917 state election, winning South Fremantle as an "Independent Labor" candidate by just six votes over Harry Bolton, the sitting National Labor Party member.
He served a single term in parliament before suffering a heavy defeat at the 1921 election, where he polled just 9.2 percent on first preferences.
After leaving politics, Rocke eventually moved to New South Wales, where he worked for Sanitarium Australia.