What is the best graduate ROTC program?

If you've got the degrees, go to OCS. Quickest way to a commission. Talk with officer recruiters for all the Services (active and reserve component) and determine where you can get the best deal in terms of start date and credit for your prior service.

70B is only available in the reserves/guard. If you want to commission as a 70B, you need to find a unit that has that paragraph/line #. You will have to go for another masters if you want to participate in ROTC since you have to be a full time student in order to participate. When component/branching selections come due, it would be a good idea to have a Letter of Acceptance (LOA) from your projected unit. This is how the process worked in my state (Ohio). You could also contact the national guard officer strength manager for your state, this is their job.
For direct commission information, please see: https://www.goarmy.com/careers-and-jobs/become-an-officer/how-to-become-an-officer-in-the-army/direct-commission.html
OCS is going to be a little tricky but possible. It would depend if you were going federal or state OCS. If you enlist in the guard as an OCS candidate , your chances of getting 70B are more likely since it's your responsibility to secure your spot. If you attend federal OCS you could get picked up for active duty which may or may not be what you want right now but you may be interested later. Jobs are also selected based on an order of merit list and you could end up in a spot you did not want.

Hope this helps.
Good luck!

Your post is somewhat vague. What are you trying to do? You mention OCS, direct commission, and ROTC.