You can contact the admissions dept directly, but honestly it would be best to contact the det and tell them. Some colleges have ROTC CoCs sit on their admissions board, thus they can help from there.
The fact is depending on the college it is not really a big chance of it swaying them if you are not a match or a safety, especially if the college is very competitive to get in from a numbers game. I.E. in VA, VT has @33K applicants a yr. for an incoming class size of 4500, with about 10K admitted. GMU and JMU follow about the same numbers.
Those colleges have more than enough match/safety applicants that the scholarship is of no importance to them.
Our DS went to UMDCP, and they too couldn't care less about the ROTC scholarship, they know they will get their money, and on top of that they also know that ROTC cadets can bolt before the start of their sophomore yr., thus for them they can truly only bank on your freshman yr. for guaranteed payment via DoD.