Can a Roth IRA Be Used As A "Stockholder" Or "Investor" Or "Own" A Business?

All of my ROTH is invested in stock, but only thrum mutual funds or stock ownership of large corporations.

As for attempting to be the only stockholder (or have the ROTH own real estate), never. Invariably the project will need more money than the ROTH has...and conflicts of interest can break the laws controlling the self-directer IRA.

It can't be done as you have stated.

Any amounts inside any IRA can be converted to a Roth IRA. However, when you do the conversion, the amount of earnings converted will be pro-rated according to the total inside the IRA. The assets of the IRA are irrelevant, they could be stocks, businesses, real estate, etc.

For an over-simplified example, if the IRA has $95,000 of contributions on 1/1/2013 and $100,000 on 12/31/2013, 5% of the IRA is earnings and 95% contributions. If you convert $5,000, $4,750 will be converted contributions and $250 will be converted earnings.

You cannot select only the earnings of the IRA to convert to a Roth IRA.

many people have their stock holdings within an IRA which they are able to manipulate to earn the most they can from those investments

I have never seen any business operations that are within an IRA

Theoretically possible but quite complex and expensive.

It is called a "self-directed IRA".

http://en.wikipedia.org/wiki/Self-directed_IRA