In lord of the flies why does roger throw rocks at the little kids?

because he doesn't really want to hurt him he was just to scared to hit him

He does this because he is testing the boundries in the new society that has been created by the kids. He does not throw the rocks directly at Henry because in civilized society that's not allowed. He is seeing if anyone will stop him in their new society.

Another interpretation might be that although Roger really wants to throw the stones directly at Henry years of conditioning by the polite society in which he was raised subconciously prevents him and makes him deliberatly throw wide of his target against in concious choice. Later, as the effects of the the distant society which raised them is increasingly diluted, Roger is able to whip and deliberately hurt other boys. It is his suggestion that Ralph should bebe hunted and killed and one is left to wonder what excesses he might be capable of in the future.

Another answer: or all of his life Roger, like other boys, has been told by adults not to do certain things, such as throwing stones at people and things. So despite his genuine desire to throw stones at Henry, with the intention of hitting and hurting the littlun, the years of 'conditioning' caused him to subconsciously throw wide of the target. Later in the book Roger overcame his 'conditioning' and allowed his true nature to blossom, with fatal results for Piggy.