Hi.,My situation is similar with you,except I did not have any interview yet. I have get the admission to the phd program,but I didn't get any fouding yet.The department told me that the RA/TA is still be selected by the professors and department. Some applicants told me that the fouding may be selected each year,so the one who paid for their first year has grant opportunity to get the RA/TA next year,which means tution waived and get paid each month.
wish you good luck.