You need to file a schedule C for self-employment. The amount that is considered compensation for purposes of a Roth IRA is your net income from self-employment after subtracting expenses and half the self-employment tax.
A 1099-NEC is not by itself sufficient. It might have been issued by mistake and you aren’t really self-employed, and it doesn’t take into account any of your legitimate business expenses. You are also required to deduct all of your legitimate business expenses — you can’t leave some expenses off your schedule C to generate a higher income for other tax purposes. That would be considered tax fraud just as much as if you claimed false expenses to lower your taxable income.
