You cannot just put unlimited amounts of annual $ into a Roth IRA... individuals over 50 years old are capped at $6500 annual contribution. (And you cannot simply transfer shares from a non-Roth IRA account into one - you need to sell them and deal with the tax consequences first, THEN you can transfer no more than that $6500 annual amount.) Which is why the best use of a Roth IRA is among the young.

This structure doesn't make it easy to accumulate large positions in a fugure mega-stock, unless of course you have the balls to buy in when it's unnaturally low for reasons you are sure amount to a screaming buy opportunity (or plural opportunities as the case may be...)

Or, if you are lucky and know what you are doing, you can trade your position into a larger one without any tax implications at all.

What Mack was describing was not a Roth IRA situation as much as utilizing the special discounted capital gains loopholes offered in the U.S. tax system to those who practice "fund management." Loopholes that were purchased at fair cost from assorted of our Congressmen and -women.