Rolling

This is the bread and butter in KOF. It's unique to KOF in a way that it replaces the two plane system created by SNK which first appeared in Fatal Fury 1. The two plane system in the Fatal Fury actually had fighting on two planes. You could knock the opponent into the next plain, therefore making the game sort of more exciting. Later SNK added the ability to actually enter the other plane without having your ass just kicked into it. (in FF1 only opponents seem to freely go back and forth into the planes). The thing is, going to the other plain was pretty neat since you can avoid some harsh attacks, say Krauser's (final boss from Fatal Fury 2) Kaiser Wave, which traveled fairly quick and was 3/4s of the screen tall.

Another thing is that if you were quick enough, you could enter the other plain, dash to the other side and slide back down to the original plane to fool your opponent and kick their ass. Rolling was kind of a variation of it.

Rolling is basically accomplished from pressing A and B together (WK and WP). What happens is your character would roll (usually) and become invincible for the duration of the roll. This was extremely good considering that it was a great tactical thing. It was a good way to avoid "fireball wars" (people just tossing fireballs all day) since the jumping element of risk was easily overcome by just pressing those two wonderful buttons. Rolling was also an effective way to get on the other side of the character. Of course rolling had it's drawbacks such as a small bit of recovery time and I think being able to thrown out of it.

You could roll back and forth. Yes.