To recognize a loss relative to your basis in Roth 401(k) contributions it would have to be claimed as a miscellaneous deduction subject to the 2% of AGI floor, but miscellaneous deductions subject to the 2% of AGI floor have been suspended by the Tax Cuts and Jobs Act of 2017 for tax years 2018 through 2025, so no, there is no way to recognize the loss. Distributions from retirement accounts are treated as ordinary income and are not subject to capital gains treatment.
