It is hard to know what is causing the numbness
in the roof of your mouth without being able to perform a physical examination. This is a strange sensation, and it is certainly worth having your primary care doctor
or your dentist
take a look in your mouth to help you figure it out.
I can think of a few potential causes.
For example, sometimes the lining of the roof of the mouth can become irritated or chafed from certain foods, especially spicy foods, citrus, and the like. This might lead to a sensation of burning or numbness while the tissue is healing. Also, smoking is a common cause of irritation in the mouth and might lead to a similar sensation.
If you have a tooth infection or a cavity that is deep enough to stimulate the nerve inside the tooth, you might experience some sharp twinges of pain or aching numbness which could spread across the roof of your mouth.
Finally, if you have any sores or blisters in you mouth, these might be signs of a viral infection, such as a herpes virus infection, which could definitely be associated with numbness.
Please get in to see your doctor at your convenience for an evaluation.