Yes, this should work because Roth 401(k) contributions become Roth IRA contributions upon rollover, which can always be withdrawn without tax or penalty, while the rest is earnings. You should get a Form 1099-R from your 401(k) provider showing the total and how much was contributions. The only caveat with this plan would be if you are still employed by the ...
Depending on whether the SECURE Act becomes law1, your children may be forced to withdraw from the Roth account faster than you might like. It changes the Required Minimum Distribution (RMD) rules.
As I understand it, the bill says a non-spousal inheritor must empty the account within 10 years of your death.
While not a tax per se, it makes your scheme ...
True, a Roth has no income tax. The tax was already paid on deposit and no more tax due.
But, the Roth, IRA or 401, still might be subject to estate tax, as it is still part of the estate for state and federal estate tax purposes. Keep in mind, the federal estate exemption is high, over $11M per decedent. State varies, by, well, state.