Dear Ms. Stevens,
Thank you for posting your request on History Hub!
We searched the National Archives Catalog and located the record series titled Carded Records Showing Military Service of Soldiers Who Fought in Volunteer Organizations During the Spanish-American War. Portions of this series have been digitized and can be searched and viewed through the Catalog. A search in the record series for 1st U. S. Volunteer Cavalry (Rough Riders) gives 1,235 results, to include the Compiled Military Service Record of Theodore Roosevelt.
We also located the Register of Commissions of U.S. Volunteer Officers, 1898 - 1901 which includes information about the commissioning of volunteer officers during the Spanish American War, to include Theodore Roosevelt and other officers of the 1st U. S. Volunteer Cavalry. Some of the other records related to the Rough Riders include the Congressional Medal of Honor File of Assistant Surgeon James Robb Church, 1st U.S. Volunteer Cavalry Regiment, the Report of Operations, 1st U.S. Volunteer Cavalry, July 1 to 17, 1898, and Casualty List, Rough Riders, July 1 to 3, 1898. Attachment to Report of Operations. These records and all other U.S. military records concerning the Spanish American War are in the custody of the National Archives at Washington, DC - Textual Reference (RDT1). Some of these records have been digitized and made available through the Catalog and others are only available as paper or microfilm. To access these records contact RDT1 via email at firstname.lastname@example.org.
We also searched online and located a digitized version of the book The Story of the Rough Riders, 1st U.S. Volunteer Cavalry: The Regiment in Camp and on the Battle Field. The book includes a section entitled “The Roster of the Rough Riders” on pages 259 through 320.
We hope this information is helpful. Best of luck with your research!