Rolling

You can while shielding perform a Roll/Sidestep or a Dodge, but you don't have to be in your shield to do them.

In order to perform a Roll/Sidestep, simply press any shield button (or while holding one of them) and either left or right. You will roll in that direction.

In order to perform a Dodge, simply press any shield button (or while holding one of them) and down and you will perform a dodging motion on the spot.

Both Rolls and Dodges have Invincibility Frames at the beginning of them (certain Rolls and Dodges have more while some have less and some are longer (though not necessarily with more Invincibility Frames) while some are shorter though not necessarily with less Invincibility Frames).

You can also use the C-stick to perform any of these tasks.