Koroilavesau grew up in Nalotu in Kadavu Province. He was educated at Yawe District primary school, Richmond High School, and Lelean Memorial School. After sixth form, he joined the Fijian Navy as an officer cadet. In his military career he reached the rank of Commander. In 1988 he started a tourism company, Captain Cook Cruises, and in 2003 retired from the Navy to manage it.
Koroilavesau was elected in the 2014 election, in which he won 1,611 votes.