If your feet roll inwards, it's because they are meant to do that naturally. The idea that such runners need special shoes to protect them is just another way for shoe companies to charge more money for their products.
Yes and no.
Pronation and supination are part of the natural gait cycle. Both are necessary in order for us to move. OVER or UNDER pronation are when people have problems. Too much of one without enough of the other can cause poor bio-mechanical alignment. Poor bio-mechanical alignment can lead to injuries. The right shoe for the right person can help even out the over/under equation and help prevent injuries.