Straight skinny on Navy ROTC time counting towards retirement (from one who is old enough to retire).
Regardless of what you may think, you are not on active duty while in Navy ROTC. At least not in the sense that the Navy views it. Therefore your four years of ROTC time don't count for squat, unlike the USNA guys who can apply those four years once they qualify for retirement (i.e. 20 years faithful service then magically becomes 24 when USNA time is added in).
Now the caveat. You can request credit for your active duty summer training time, but the burden of proof is on you. You can't just say "hey, everyone had to cruise, so credit me for 2 extra months of active duty." You need to provide a copy of your endorsed orders for each training period, so they can account for those days. Or a copy of the pages out of ship logbooks showing arrival departure dates. Tougher to do if you went to a squadron, because no squadron SDO gives a crap about the logbook unless there's a mishap, so for sure they didn't bother to record the arrival of a midiot on summer cruise.
Learning point: Keep a copy of EVERY piece of paper the Navy gives you that remotely pertains to pay or medical stuff.
If you retire off of active duty, those two months won't mean much. But if you retire out of the reserves, an extra two months of points equates to 1/6th of a year, or an additional 1.25% salary multiplier when figuring out your Reserve pay / pension. This is higher math requiring a separate thread, and if you're worrying about how much money you'll be making at age 60, you're worrying about the wrong thing. Focus on getting laid and not washing out of flight school...in that order.