By "SEP" I assume that you mean self-employment tax, not a SEP contribution.
Being in the 22% tax bracket, I'll assume that eligibility to make a Roth IRA contribution is not limited by modified AGI.
$3,000 of net profit from self-employment means $424 of self-employment tax. Subtracting the deductible portion of self-employment tax, $212, from $3,000 leaves net earnings of $2,788 available to support a Roth IRA contribution.
