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The Form 1099-R should report the distribution from a ROTH IRA if early by using code "J" in box 7. I am not aware of another code that would exempt the distribution from an early withdrawal penalty.

The instructions to Form 5329, Additional Tax on Qualified Plans, mentions that you can exclude the 10% penalty on early pension plan distributions if you are permanently disabled and that a medical determination of that must be made. However, there is no mention of a need to file a copy of that determination with your tax return. It appears it will suffice to keep a written record of the determination in case you are audited on the matter at a later time. The determination letter you are referring to may be for the pension plan administrator to authorize the early distribution of funds to you.

You indicate that you are permanently disabled after you enter your Form 1099-R in TurboTax and on that basis Form 5329 will be populated and included with your Form 1040 when you file your tax return: