An employer plan (401k, 403b, etc) is NOT an IRA, and the contribution rules are completely separate. For 2025, the limit for elective salary deferral (your contribution) to a qualified workplace plan is $23,500, or $31,000 if you are over age 50. The limit for all qualified plan contributions (employee plus employer) is $70,000. It does not matter how you split this workplace contribution between pre-tax and after-tax (Roth account).
Those limits are completely separate from IRA limits. If you are under the income threshold for a Roth IRA, you can max out out your workplace plan (pre-tax or Roth) AND max out your Roth IRA. If you are over the income threshold for a Roth IRA contribution, you can still contribute the maximum through your qualified workplace plan.
