You likely did not over-contribute. The $19,000 employee contribution limit to the 401(k) and the $6,000 limit to the IRA are separate limits, except that if you made $19,000 of elective deferrals to the traditional account in the 401(k), that reduced the amount that your employer reported in box 1 of your W-2. If your only compensation is compensation reported on Forms W-2, your Roth IRA contribution is not permitted to be more than the amount of your compensation in box 1 of those Forms W-2. Also, depending whether or not your MAGI for the purpose was too high, the amount that you are eligible to contribute to a Roth IRA may be less than $6,000.
