These possible candidates with "Riley" variant spellings are listed on the 1860 Census of Frederick County, Va.
J.C. Riely – age 24
James P. Riely – age 19
W. B. Riely – age 17
Luke Reily – age 45
John W. Riely – age 21
Moses Riely – age 53
I believe the Jesse Scouts were originally recruited from Company K, 1st West Virginia Cavalry, so your man may be Sergeant James (H or R) Riley of that unit.
A gentleman named David Phillips may be the expert you seek. He is the author of Tiger John: The Rebel Who Burned Chambersburg. A contact e-mail address can be found at:
http://www.jessiescouts.com
Click on "$500 Bounty" for an email link.