Assuming an early withdrawal you only pay income tax and a 10% penalty on the earnings. 

The $17,000 threshold is for whether the GIVER of the gift has to file a gift tax return.  "Gift Tax" is somewhat of a misnomer.  Even though a gift tax return may be required, for individual  gifts over $17,000, very few people ever actually pay federal gift tax. The purpose of the gift tax return is usually only to document a reduction in the allowable estate tax exemption.
See https://turbotax.intuit.com/tax-tools/tax-tips/Tax-Planning-and-Checklists/The-Gift-Tax-Made-Simple/...  

What is your age, and how long ago did you open the Roth IRA?  Depending on the answers to those questions, you might owe income tax on the withdrawal, no matter what you do with the money.  

Your son never owes tax on a received gift, although the giver must file a form 709 to report the gift.  (Gift tax is not owed unless your lifetime total of all gifts is more than $13million, but large gifts must be reported so the IRS can track them against your lifetime limit.)