If you are enrolling in UTSA as a graduate student you must complete the ROTC advanced course or MSIII and MSIV course. You can enter the Army ROTC Advanced Course by completing the Leader's Training Course held at Fort Knox, Kentucky, during the summer.
Talk to your campus Military Science department about other ways to enroll in Army ROTC and the incentives available, including opportunities to compete for two-, three-, or four-year scholarships. Apply for scholarships on the left hand tab Scholarships under "Admissions and Scholarships" and select Graduate Students. Also, look into the SMP (Simultaneous Membership Program).