ROTC IGEP (Immediate Graduate Education Program)
http://www.usna.edu/AdminSupport/Instructions/1000-1999/1520-2y.pdf
The link above takes you to the current instruction for USNA on IGEP (post-grad) programs. Of interest, if you slog though it, there are some programs at Naval Postgraduate School where ROTC midshipmen are eligible.
This link takes you to one of the many Naval Postgraduate School entries I found that mention ROTC grads as being eligible for a Master's program after commissioning. See page 2.
http://www.nps.edu/Academics/GSEAS/MAE/Brochures/MAE Brochure 2008.pdf
fishbowl, Don't rush to make "can't go to grad school right after graduation" a huge weighting factor when considering ROTC vs. SA.
The vast majority of midshipmen and cadets head right out to their warfare specialty, because that's what junior officers do - head to the operational world and start up the professional qualification ladder. All the services have a number of programs and opportunities for the Master's degree, after those first operational tours focused on professional warfare qualifications. And, it's quite true, if a junior officer goes to a grad program for a year or two, then to the ship, flight school or sub pipeline or whatever, they are indeed that number of years behind their peer group professionally. Ditto Marines. Yep, it's worth doing if they are on the Rhodes, Fullbright, MIT, Stanford, Harvard or other prestigious, life-long value in the resume programs, but they will come aboard their first operational command knowing squat compared to others of their commissioning year group, and will have to work extremely hard to catch up. Of course, later on, when their peers are getting their Master's, these JOs have the opportunity to do something else interesting because they already have their degree. One thing is for sure - only the very top of the class at SAs have an opportunity to apply for these, and I imagine it's the same for ROTC. They are the exception, rather than the rule.
OK, I have frayed the end of this poor thread enough, I apologize.
P.S. And just because something is true this year, does not mean it will be true in 4 years. The "needs of the Navy" (or whatever Service) govern everything. If they needed every JO to go right to the Fleet, the graduate program would be turned off in a heartbeat, because operational needs dominate. That's highly unlikely, but things happen. As an admiral I used to work for said, "If Moses didn't bring it down from the mountaintop carved in stone, every regulation, directive, instruction and program in the Navy can be written in Jello and is thus changeable."