When you get through Army ROTC or NROTC, can you do 8 years Reserve or is there a minimum of 4 years active?

You will have a 8-year service obligation upon commissioning from ROTC. If selected for active service, you will have to do a minimum of 3 years of active duty. This depends on if you had military scholarship. If so, you will have at least a 4 year obligation depending on the amount you received for school. If you want to serve 8 years in the reserves, you can get a guaranteed reserve commission, but this is usually worked through your reserve or National Guard unit. We only had one person do this, but when he changed his mind, he wasn't allowed to go active duty because he already had a contract with the Reserves.