What is the selection rate for ROTC cadets getting active duty Army?

Robert S Worst case you can join a reserve or guard unit with the branch you want and volunteer. If you are competitive, you can pursue AGR or ADSO and have another chance at AD.
God Speed!

If you have a solid OML score then you’ll basically get what you want (besides maybe aviation because it’s super competitive). Everyone in my graduating class got their #1 branch choice and their component of choice. If you don’t get active when they get released you can apply for an ADSO which will extend your service but will give you a much better chance of locking down what you want.