Even if you do not wish to make the Army your career, Army ROTC gives you credentials which give you a competitive edge. The answer to this question is no. There are several different ways a student can meet the requirements to become a commissioned officer. ROTC is broken down into two courses, the basic course and the advanced course. The combination of these needed to be commissioned varies with the individual.
Students enter the basic course anytime between their first and third term of college.
This entails a 1 hour lecture, a 1.5 hour leadership lab, and 1 or 2 hours of physical training. Students who enter in either their second or third term need to enroll in the military science classes missed by not being enrolled earlier. This does not mean an additional 3.5 hours, however. It means only the extra 1 hour lecture. Many students pursue this option, and it does not significantly increase students' work loads.