Yes, you can name different beneficiaries for each of your Roth accounts.
On the Roth account you are leaving to your wife, yes, she can roll that over to her own Roth IRA as a spousal rollover.
Since she now becomes the Roth IRA owner, like all Roth IRA owners, she is not subject to any required minimum distributions (RMDs) during her lifetime, so she can keep these Roth funds growing tax free for the rest of her life. If she does need any of the funds, she can withdraw them at any time, and in any amount she wishes. Those distributions will almost always be free from income taxes to her.
Once she does a spousal rollover of the Roth IRA you are leaving her, there is no 10-year rule because the Roth IRA is no longer an inherited IRA and is instead her own Roth IRA. Even if she decided not to do a spousal rollover and kept the account as an inherited Roth IRA under the SECURE Act, a surviving spouse, like your wife, is what the tax law calls an Eligible Designated Beneficiary (EDB), meaning that the surviving spouse is exempt from the 10-year rule.
The 10-year rule will mostly apply to nonspouse beneficiaries, like your son. Under that rule, the entire inherited IRA (or Roth IRA) must be withdrawn by the end of the 10th year after death, but the distribution will likely be income tax free, since this is a Roth IRA.
That 10-year rule gives your son (and other nonspouse beneficiaries) good tax planning flexibility during those 10 years after death. There are no annual RMDs for your son during any of the 10 years after your death, except that whatever the balance is at the end of the 10 years must be withdrawn. Because inherited Roth IRA funds are likely to be completely tax free when distributed, one potential strategy is to let the earnings grow until the very end of the 10-year period and then take a tax-free distribution of all the funds. Remember, your son only gets to use the 10-year rule if he is named as beneficiary on the beneficiary form.
Once your wife inherits, she should immediately name a beneficiary, which may be your son. This way, your son will eventually inherit those funds and be able to use the 10-year rule.
Since you did not yet roll this account over to your own IRA, you are treating this as an inherited IRA, which you can do. Under those rules, you are not subject to required minimum distributions (RMDs) until your deceased husband would have reached age 72. You didn't say how old he was when he died, but that won't matter this year. Normally, if your husband were older than 70 1/2 (under the pre-2020 tax rules), you would have been required to take an RMD this year. But for 2020, due to the coronavirus pandemic, the CARES Act waived RMDs due in 2020.
You are probably better off taking ownership of your husband's IRA by doing a spousal IRA rollover. The account will now be your IRA and then you can delay any RMDs until the year you turn age 72 (the SECURE Act raised the RMD age from 70 1/2 to 72).
Assuming your husband was older than you, this will give you more years before your RMDs will begin. This way, unless you need to withdraw the funds earlier for expenses, your Social Security benefits will not be impacted by any RMD income until you reach age 72.
IRA distributions are still taxable. Nothing changed there, otherwise everyone would have withdrawn everything from their IRAs tax free! What you are probably referring to is the CARES Act, which waived RMDs due in 2020. However, if you took your RMD in January it is still taxable. The IRS gave people until Aug. 31, 2020, to return any unwanted 2020 RMDs, removing the tax bill on those. Maybe that is what you are referring to as RMDs not being taxable this year.
If you did not return the RMD funds you withdrew in January by the August deadline, you can no longer return them, so you will owe the tax on those funds. Other IRA funds can always be converted to a Roth IRA, but you will owe the tax on any taxable IRA funds you convert.
However, if you were affected by the COVID virus either by being sick or having a loss of income for either you, your family or members of your household, then that RMD you took in January can still be returned. You would have three years to return those funds by treating that withdrawal as a coronavirus-related distribution if you qualify by being affected under the sick or loss of income conditions.
Ed Slott, CPA, is one of the nation's top experts on retirement plans. For more than 30 years, he has educated both consumers and financial advisors on retirement tax-saving strategies. Most recently, he published Ed Slott's Retirement Decisions Guide: 2020 Edition and is the host of several popular public television specials, including his latest, Retire Safe & Secure! With Ed Slott. Visit www.IRAHelp.com to learn more.