Lisa, you can access a roster of the Rough Riders, the 1st. U.S. Volunteer Cavalry, on the internet. I used 'google'and typed in Rough Riders Roster. I did not see your relative listed. Sometimes, a loved ones military service gets embellished over the fog of time and retold family stories. It is possible that he served with honor in one of the other units. I had that happen in my family. My grandfather was alleged to be with Teddy Roosevelt (because that is who most people remember in connection with the war) whereas he was a US Marine who participated at the Landing At Casilda. If you find that certificate again it may provide more data to narrow down your search. Good luck with it!