What should I do if I suspect that someone at a dental office who does xrays is actually not licensed to do so?

DDS, DA, Hygienist. In dental offices, if you need a radiograph (x-ray) --either the dentist will take the x-ray or well trained dental assistants or hygienists, will take the x-rays as well as perform a variety of necessary dental procedures that are allowed by the laws of your state. Talk to your dentist, if you have questions.
Ask. Talk to the dentist and ask. However it is usual practice to have an assistant take x rays. The vast majority are trained to take radiographs.