My family owns FRFHF in both taxable and non-taxable accounts (IRA's). The taxable accounts are subject to the 15% withholding, which in turn can be used to reduce your US Tax on qualified dividends (ie. you shouldn't have double taxation) -- the 15% withholding is generally less than you would pay in US dividend taxes (although not always).
The shares held in the IRAs benefit from the US/Canada tax treaty - so, there is no withholding, similar to dividends received from US domiciled companies. Not sure what happens with Roth IRAs. I use Fidelity and they manage this process, other brokers/custodians require you to fill out a form.