QDRO's do not apply to IRA's QDRO's only apply to pensions or retirement at are covered by Employee Retirement Income Security Act (ERISA) act which is most employer plans.
Any IRA taxable IRA distribution (if over age 59 1/2 Roth distributions are not usually taxable) is the responsibility of the IRA owner on their tax return. The divorce decree should have specified who was to pay the tax and if the amount given to the other party can be reduced by any tax due. That is a question for your divorce attorney.
The split of the Roth IRA incident to divorce should have been done by non-reportable trustee to trustee transfer to avoid any distributions. Since a Form 1099-R was issued, there was a distribution and the recipient of the Form 1099-R was the recipient of the distribution and is the one responsible for the tax consequences.