A Roth IRA in Spain is not recognized as a retirement pension account like a 401k IRA. It is considered and investment account. As such one would be taxed at the savings income rate on the dividends, capital gains, and interest that the fund reports...annually.Â
So, if I begin my tax residency in Spain on Jan1 with €100,000 in my Roth IRA, that is the starting principle. If, in one year that fund earns €2000 in dividends, I would be taxed on that €2000 at the savings income rate (not PIT).
If I take out €10000 from the IRA (let's say to buy a car) it would not be considered a distribution as income because it is not a pension... it is considered principle and the "distribution" will not be taxed. I would still only pay taxes on whatever dividends accrued by the end of the year. (It appears from my statement that the only source of income to the fund is dividends...not capital gains or interest... easy to find, report, and track)
In addition, I do not have to pay the dividend taxes directly from the Roth IRA. I can pay them from savings. Thus, I am not pulling money out of the Roth and paying taxes with future compounded earnings . I can continue to compound the entire Roth investment tax sheltered in the U.S.  Also, if I should change my mind and move back to the U.S., I would still have a Roth IRA as a sort of safety net.
Initially, I thought of taking the entire Roth distribution and moving it into a money market account or investment mutual fund before moving to Spain. Now I am thinking of keeping the Roth, paying the tax on annual dividends, and consider what would be called a distribution as a savings withdrawal rather than an income.
I'm also thinking that I should use my Roth IRA as "tax free income" and draw it down before touching my regular IRA. This allows the funds in the regular (and larger) IRA, which would be taxed as income, to continue compounding tax sheltered.Â
This is sort of stream of consciousness thinking. I'm open to suggestions, information, and ideas.  The only professional advice in this is the fact that a Roth is considered an investment and not taxed as a retirement pension.