[1] However, the younger Rosa rarely referred to himself as "Jr." Educated at the Roman Catholic College of ʻĀhuimanu and later Honolulu's Royal School under Anglican Rev.

[3] After taking a two-year career sabbatical to study law, he passed his exam in October 27, 1884, and was admitted to the Bar.

At Rosa's appearances, he spoke in the Hawaiian language and expressed support for the new Bayonet Constitution, but disdained how Kalākaua had been forced into signing it.

He denounced both the Honolulu Rifles and the Reform Party of Hawaii for their actions in obtaining that constitution, and for what he purported were later illegal exchanges of money after the document became the law of the Kingdom.

[5] In October 1887, Kalākaua appointed him as his private secretary and Vice Chamberlain of the Royal Household, where he held the rank of Major.

[6][7] During the February 1890 general election, Rosa ran unopposed on the National Reform candidate for Representative of Oahu winning a seat in the legislative assembly.

[12] Judge S. L. Austin of the Third and Fourth Circuit courts died suddenly in 1896, and Rosa was appointed as his replacement under the Republic of Hawaii.

The funeral was held on the same day at the Cathedral Basilica of Our Lady of Peace officiated by Bishop Gulstan Ropert, and he was buried at the Honolulu Catholic Cemetery.

[2][13] He and his friend, former Minister of Interior John F. Colburn, were arrested in March 1898 for driving their carriage into a fish market, claiming they were trying to get the open-topped vehicle out of the rain.