I truthfully can tell you almost nothing about life at W&L as an ROTC cadet- other than that you will be going to VMI for your ROTC classes. As an ROTC cadet I suspect you might find yourself a little like the odd man out when surrounded by VMI Cadets. It's just my suspicion but I do know VMI pretty well so I can imagine that the few Non- VMI cadets who are taking ROTC are sort in there own very small orbit with not a lot of interactions outside of the formal ROTC classes with their VMI brethren.
However- there is a lot more to your college life than ROTC and my take on W&L is extremely positive. It's a lovely and highly regarded school, where you will actually get a chance to appreciate life in a charming southern town. W&L has got to be "Fraternity central" and I think that they have a pretty good social life there- and a really solid academic reputation. I have some family members who went to W&L either as undergrads or as Law students- never heard anything other than glowing comments about their time in Lexington.
Good luck