De Rosenroll was born December 4, 1857, in
Castellamare, Kingdom of the Two Sicilies, to Rudolph and Margaret de Rosenroll. He was descended from Swiss nobility on his father's side, though his line had been absent from Switzerland since 1806. When Anthony was three years old, his father was killed at
Palermo while fighting for
Giuseppe Garibaldi during the
Expedition of the Thousand; his family took refuge in Malta for much of the rest of the rebellion. Returning to Italy, de Rosenroll was taught by tutors in
Naples, and ultimately graduated from the
University of Naples in
civil engineering. He spent several years working for the British colonial governments in what is now Australia and New Zealand in this capacity, before voyaging to the United States to visit his sister. From there he came to Winnipeg in 1895, ultimately becoming one of the first residents of
Wetaskiwin in 1896. There he married Ida Eberhard, with whom he had three children: Arthur (1896–1971—born in
Ollon because of his father's distrust of the young Canadian medical profession), Edgar (1897–1968), and Richelda (1898–1944). De Rosenroll involved himself in many business ventures. The first of these was a ranching enterprise, in which he initially partnered with Scandinavian settler Thomas R. Jevne and later founded the Rosenroll Ranch near
Hay Lakes. Other ventures included the Rosenroll Lumber Co. Ltd., Rosenroll Dairy/Wetaskiwin Creamery, a coal mine, and Rosenroll Ltd., which dealt in real estate and insurance. De Rosenroll was a prominent citizen of his young and growing town. In 1896, he was made a
Justice of the Peace and a
notary public. Wetaskiwin's Rosenroll Street and nearby
Rosenroll were named in his honour (though the former was eventually re-designated with a number, and the latter was renamed to Bittern Lake in 1910). He was an active
Presbyterian and a
Mason. ==Political career and later life==