While in Alabama, he had transcribed the speech in which Jefferson Davis vowed to “carry the sword and torch through the northern cities” and sent it to the Associated Press. In a contretemps between Davis and Rosewater over this speech many years later, Davis intimated (so Rosewater maintained) that “from the information he could procure, was a northern spy and not admitted into [the good secession society of northern Alabama.” When Union forces retook Nashville during February 1862, Rosewater offered his services, supervising the restoration of the army's telegraph lines across the Cumberland Gap. A brief visit to his family in Cleveland followed, after which he enlisted in the United States Army Telegraph Corps, staying with General John C. Frémont throughout his West Virginia campaign.