If you're interested in the ARNG find the units near you, or with the helicopters you want to fly, and contact the S-1. Tell him your situation and ask who to talk with. Open the door and see what the aviation unit has to say.

Recruiters will tell you what they need.

You may be able to complete your degree in ROTC and enter a commisioned slot but the S-1 will know what the actual needs are. You may need to contact more than one unit to find a need for commisioned officers.