Hey, I'm looking into The Citadel for next year as well.
From what I understand (website, and a friend who graduated from there), Cadets can graduate early. If you graduate early, you can still come back to graduate with your class. You could also just use those credits to pursue a second major or minor. Now, I don't know how the ROTC scholarship will impact that, but I'm sure you can find out by emailing the office of admissions or the registrar.