Both traditional IRAs and Roth IRAs offer some benefits when it comes to taxes and estate planning, but a Roth IRA comes with one benefit the traditional retirement account doesn't. Both plans let you put money away for retirement while reducing your tax burden, and you can use them both to pass some assets on to heirs without going through probate.
The way you avoid probate through a retirement account is to designate a beneficiary specifically for that account. You do this by completing a beneficiary form with the institution that holds your account. In many cases, the institution has you complete the form as part of setting up the account, but if you don't remember doing so, you can double check to ensure you have a beneficiary designated. You can also make changes to your beneficiary designation as needed -- check with your financial institution for information on how, when and how often you can make such changes.