DD (AROTC) studied abroad in Mexico for spring quarter her MS-II year. It is a requirement for her major, and she was careful to choose a program affiliated with her university so her scholarship could be applied to the tuition. In her case, I think she studied along with the ROTC class for that quarter and took the same MilSci on-line final.
I think DD's advice would be to start asking questions, identifying programs, and planning when it will work to go aboard early on in freshman year. In her case, MS-II year worked best, and it arrives surprisingly quickly after that initial freshman drop-off.
Regarding studying aboard and ROTC, DD found she tended to get different answers depending on who she asked so it took a while put all the pieces together. There was also paperwork that had to be approved all the way up the chain to Cadet Command, and there might be some "hotspot" destinations around the globe which would not be approved.