The IRS makes its own determination as to whether you are considered disabled for the exception to the early-distribution penalty from these accounts. VA and SSA disability statuses are determined differently.
From IRS Pub 590-B:
You are considered disabled if you can furnish proof that you cannot do any substantial gainful activity because of your physical or mental condition. A physician must determine that your condition can be expected to result in death or to be of long, continued, and indefinite duration.
The penalty only applies to the taxable portions of distributions from your Roth IRA or TSP. From your Roth IRA, your original contributions are distributed first tax and penalty free regardless of the reason for the distribution. Distributions from your TSP would typically be entirely taxable and subject to the early-distribution penalty unless a penalty exception applies.