I agree with gojack it can be an issue, because ROTC cadets get up O'dark thirty for PT, thus if the roommate is a night owl it can become an issue.
That being stated, our DS had no problem with his non-cadet roommates... they respected the fact that 2x a week he would be getting up at 5-5:30 for PT. They were quiet after a certain hour, and he was quiet when he woke up so not to disturb them.
It really does come down to a respect issue. Our DS opted for his 1st 2 yrs not to live with ROTC people. He wanted to experience college life. It is now that he is living with ROTC cadets (off campus) because these are the people he has become close friends with after being there for 2 yrs.