It was called The Halcyon, and, failing to prove remunerative, was abandoned for the study of the law, Roselius supporting himself during this time by teaching.

His legal studies were pursued in company with his friend, Alexander Dimitry, in the office of Auguste Devesac, beginning in December 1826 and terminating in March 1828, at which time he was admitted to practice by the Louisiana Supreme Court, consisting of Judges Martin, Matthews, and Porter.

His love of the civil law became a passion, and soon placed him in the front rank and eventually at the head of the Louisiana bar.

During the same decade he was honored with an invitation to become the law partner in Washington of Daniel Webster, which he, however, declined, preferring to remain in the South.

His hand and purse were always open to the unfortunate, and one of several visits to his native land was for the sole purpose of aiding some of his less prosperous kinsmen.