No I,m not a history buff but do like to look up military things. I found what information I gave you on the web site www.spanamwar.com/geneaol.htm. I think the Rough Riders were the first group of volunteers and they were from all different states. Then each state had their own regiments I suppose they were the National Guard of that time or like it. I hope this makes sense and doesn't mix you up. But it sounds like your relative was a volunteer to the Rough Riders and not to any certain ste unit. I suppose if you coud find a Rough Rider Roster you would find him there.