That would be up to the Army to decide, but you'd probably be stuck until you were done with your commitment and put in for an interservice transfer. Apply for all the ROTC programs, see what you are accepted for, and then apply to a school with that program. You've got to be very open minded in the military, and it might as well start with the variety of universities that you can attend. Don't limit your future and long term goals for four short years... Unless you are talking ivy league or some top-tier-best-of-the-best university program.