SteslaS - the ROTC scholarship pays for your tuition (R&B too I think) while you're in school, so you don't have to. You can apply as a high school senior and know your scholarship status before you enter college. Scholarships are awarded for 4 years, or if you apply after you are a college student you can apply for 3 or 2 year scholarships.
Google rotc and you can read about the program on the Army's website. If you have questions about applying or want info about rotc options start a thread here and I'm sure there are lots of people who are familiar with the program and can give you good guidance so you can make the best choice to meet your goals and interests. Here's a forum on ROTC issues that might help you too
ROTC - United States of America Service Academy Forums
Good luck with your college search!