What happens taxwise if I purchase shares of a land oil trust which would normally incure taxes in the state of origin, but in a ROTH IRA?

It would help to have a specific trust to look at to see how they tax it. If it is taxed from distributions before distributions are made, there is no way to get a tax deduction or tax credit for that in a retirement account.

A prime example is that years ago I had Canadian gas/oil trust shares. Suddenly Canada realized that they were not getting tax money from distributions paid for shares on US stock exchanges and began taxing distributions up front, before they were distributed. Due to a tax treaty with Canada, that was taxed at 15%, which was the same as the 15% that US charged for qualified dividends. So in a taxable account, you could get foreign tax credit for the 15% Canadian tax deducted from the 15% US tax you would normally owe on those distributions (considered qualified dividends).

But in an IRA or Roth IRA, you are not paying any federal tax on those distributions while they are in your retirement account. So there is no federal tax deduction for state tax deducted from distributions that were not federally taxed. In other words, there is no federal tax deduction for federally untaxed money. So in my Canadian gas/oil example I just had to eat the Canadian tax for shares I had in my IRA or Roth IRA.