Tom:

There may be hospital and other records from Fortress Rosecrans at the National Archives that mention your soldier. They're tough to sift through and probably won't be more specific than his individual records.

Van Cleve was no longer in command at the fort in December 1864. General Lovell Rousseau was in charge by then. I wonder if your man was assigned to Van Cleve as an orderly while convalescing and then returned to his regiment in time for active participation in the Battle of the Cedars.

General Rosecrans was no where near his namesake fort when the Battle of the Cedars took place. The fort was named for him during its construction after the Battle of Stones River (12/31/62-01/02/63). Rosecrans had long since been relieved of any significant command duties in the army.