Anything you deposit to the traditional IRA in excess of the gross amount distributed from your traditional 401(k) would be a new, regular contribution to your traditional IRA subject to the annual contribution limits for regular contributions. Anything that you deposit to the Roth IRA in excess of the amount distributed from the Roth 401(k) would either be a taxable Roth rollover from the traditional 401(k) (and only the remainder of the gross distribution from the traditional 401(k) would be available to roll over tax-free to the traditional IRA) or a new, regular contribution to the Roth IRA subject to the annual contribution limits for regular contributions.
The IRA custodian will require that you identify which contributions are rollover contributions of amounts distributed from the 401(k) and which contributions are new, regular contributions. If you mistakenly roll over more than permitted or make new, regular contributions that are more than permitted you will be subject to a 6% penalty on the excess contributions each year they remain in the account.
