Not sure how the Army system works, but I'm just finishing the Air Force version.
AFROTC is designed to be a 4 year course, though you can do 3 year and for high demand majors, 2 years.
Your first two years are a learning phase. You learn things like military structure, drill, uniform wear, ect. You are preparing for Field Training which comes between your sophmore and junior year.
FT is similar to basic training with a few key differences: at BT you are expected to know nothing, and are taught what you need to know. At ROTC FT, you are expected to know everything you should know BEFORE you show up. FT is more of test of your leadership and followership skills rather than an indoctrination exercise. I had a few prior enlisted guys in my flight at FT, including an Army guy, and they all said that ROTC FT was much harder than basic training because of the level of mental stress they put on you and still expect you to perform.
Your junior and senior years you are the leader of the cadet corps. The cadet corps is organized like an active duty AF wing, and the juniors and seniors fill the leadership positions in that wing.
Throughout ROTC you also have an academic class. Freshman and Sophmore year the class meets once a week and you get 1 credit hour for it. Junior and Senior year the class meets twice a week and you get 3 hours for it. Classes vary by the year: Freshman year is about AF organization and function, Sophmore year is about AF and aviation history, Junior year is administration and managment, and Senior year is National Security Affairs and Prep for Active duty.
Finally, you have 2 hours per week of PT that is required.
The spring of your junior year is when you generally find out what job you will have once you commission. 95% of cadets commission and go on active duty. You would only go reserve if you were defering service to go to med school/law school. Your job selection is based on how you are rated in ROTC. You incur an 8 year service commitment after ROTC. You serve 4 years on active duty and 4 years on the reserves. The exception to this is if you are going to be a Pilot or Combat Systems Officer (used to be called Navigators) Pilots have a 10 year commitment after training and CSO's have a 6 year commitment after training. Both Pilot and CSO schools last a year, so do the math.
DO NOT DO ROTC AND EXPECT TO COMMISSION INTO THE RESERVE!!! UNLESS THE AIR FORCE DOES NOT NEED YOU, YOU
WILL GO ON ACTIVE DUTY AFTER GRADUATION!!!
As I said, I am just finishing up ROTC and will commission in May. I can honestly say that I have learned more in ROTC than I have anywhere else for my entire life.
If you have more questions, ask me or check out my detachment's webpage
here or contact the detachment at 305-284-2870. You can get general info about the program that will apply to all det's.