You are not permitted to claim a deduction for this loss. If you distributed all of the money in all of your Roth IRAs and had unrecoverable basis in Roth IRA contributions and conversions, you would have a miscellaneous deduction subject to the 2%-of-AGI floor. Miscellaneous deductions subject to the 2%-of-AGI floor have been suspended through tax year 2025.
If you have other money in Roth IRAs, I would suggest maintaining a Roth IRA balance until at least 2026 when miscellaneous deductions subject to the 2%-of-AGI floor are scheduled to become available again and, if the value in your Roth IRAs at that time is less than your basis in Roth IRA contributions and conversions, consider distributing all of the money from your Roth IRAs so that you can claim the deduction. Of course if your balance in your other Roth IRAs is greater than your basis Roth IRA contributions and conversions, there is no deduction to be had at all.
