I have deleted the answer that I posted earlier. It might not be correct. Hopefully someone who knows more about it that I do will answer your question.
Distributions from a Roth 401(k) are a proportional mix of contributions and earnings, so unless the investments lost value, some amount will be taxable and subject to early-distribution penalty unless the taxable portion is rolled over. To avoid the tax and penalty you can either receive a distribution and roll the taxable portion over to a Roth IRA (rollovers consist first of the taxable portion of the distribution) although there would be some mandatory tax withholding doing this, or, probably preferably, asking the 401(k) plan to directly roll the entire distribution (perhaps the entire Roth 401(k)) over to a Roth IRA (avoiding mandatory tax withholding) and then take out just your contributions using the Roth IRA ordering rules which dictate that your original contributions to the Roth IRA come out first, tax and penalty free.
does your previous employers plan even allow for such distributions?
Any portion of a nonqualified distribution that comes from earnings will be subject to the 10% penalty unless the following requirements is met - this is for your situation. there are also others where no penalty is involved
the distribution does not exceed the amount of medical expenses that you can claim as an itemized deduction for the year.
this means that the qualified portion is the total qualified expenses reduced by either 7.5% or 10% of your adjusted gross income (AGI) say your is $40,000 and your medical expenses are $35,000 if the 10% applies the $35k must be reduced by $4k leaving only $31k that can be withdrawn penalty free.