University of Michigan is approximately 110 strong (one cross-town included, Eastern Michigan University). This is NROTC. I don't know the sizes of the other ROTC programs.
For Army I would say that's medium size. In past years with all of our satellite schools we had over 100 cadets and my host school was a rather small D3. With scholarship cuts and the "trimming of fat" many wishy-washy people stopped showing up or less people became interested because of the lack of funds.