Does a rollover from RMD to Roth get taxed twice?

First: in case you don't know, in 2020 you do not have to take an RMD if you don't want to. So, consider whether you want to!

If you decide to do this, regardless, you're not taxed extra for putting something into a Roth account. See this Investopedia article covering the rollover from RMD to Roth concept for more details. Do make sure that you have the required earned income, and meet the other requirements.

But no, you would not pay more taxes from the rollover than you would just taking the money and spending it; you pay taxes once, but not more.

Let's use correct words. Rollovers from a Traditional IRA to a Roth IRA require payment of appropriate income tax on the amount rolled over (no 10% penalty for those under 59.5 years of age when doing the rollover) and can be done any time without regard to whether the IRA owner has earned income in the year of rollover or not. However, Required Minimum Distributions (RMDs), which start at age 70.5 for regular Traditional IRAs (and sooner for Inherited IRAs) are specifically not allowed to be rolled over into a Roth IRA or Roth 401(k) for that matter. People taking RMDs must request a distribution over and above the RMD amount, and can roll over only the excess into a Roth IRA if they so desire. What the OP is proposing to do is to take some (or all) of his Required Minimum Distribution and put it into his Roth IRA. This is not a rollover, regardless of whatever investopedia might be saying -- it is a new contribution to the OP's Roth IRA -- and is thus subject to the rules for Roth IRA contributions which include having compensation (earned income (W2 or self-employment), sales commissions, etc) and being limited to the lesser of the compensation and $6000 ($7000 for the OP since he is above 50).

That being said, for 2020 only, (thus far, but possibly subject to extension), the RMD has been waived and so whatever the OP wishes to roll over from his Traditional IRA to his Roth IRA is fine. He will need to pay income tax on the amount of the distribution but the whole amount can be rolled over into a Roth IRA, no problems. This is best done as a trustee-to-trustee transfer (easiest if the trustee is the same for both IRAs, and only slightly more difficult if the trustees are different companies). If the "RMD money" has been taken out less than 60 days ago, it might be possible to arrange to have it sent to a new trustee as a rollover contribution to a new Roth IRA account (or put it back into the Traditional IRA itself (as the law allows for 2020) and taken out again as a rollover into the Roth IRA). But if the RMD money came out earlier, the OP is SOL unless he has compensation, etc. and the contribution limits come into play.