Parent pays Nondependent Student room and board

If the student is not being claimed as a dependent on your tax return you cannot claim any education expenses on your tax return.

Q. Are we able to deduct any of this room and board on our (parent) taxes?

A. No. Room and board (R&B)  are not claimable expenses, even if he was your dependent.

However, R&B are qualified expenses for a 529 plan distribution. Even if the student does no actually pay anything. He may claim the lesser of the  actual expenses or the the school’s R&B “allowance for cost of attendance” for student living with parents. This number is available from the school. 

Side question: why isn't he your dependent. 

The treatment of expenses paid with distributions from Sec. 529 plans and Coverdell ESAs in the dependent support test is uncertain because of the dual nature of these college savings vehicles and a lack of IRS guidance. The consensus among tax experts is that it is parental support, because the parent is the owner of the plan.  

References:

https://www.savingforcollege.com/articles/the-impact-of-529-plans-on-claiming-a-dependent

https://proconnect.intuit.com/community/tax-talk/discussion/529-plan-distribution-and-support-test/00/80039