Rosevear attended the local public school before beginning work in the timber industry, where he became known as a skilled tradesman.

[1] Rosevear became involved in the labour movement at a young age as a member of the Timber Workers' Union.

He lost his job and led the Leichhardt Unemployed Workers' Relief Movement during the Great Depression.

He gained a reputation as an inflexible Speaker, accused by the media and the Opposition of partisanship; journalist E.H. Cox claimed that he was "frequently drunk in the Chair".

Rosevear continued to be influential in caucus, and it was rumoured that he hoped to succeed Ben Chifley as party leader, but his "taste for grog" was seen as a disqualification by some.

In the 1949 election the Chifley government was defeated by the Liberal/Country Party coalition led by Prime Minister Robert Menzies and Rosevear lost the Speakership.