The roster lock is a lock on the number in your clan not the names . Example if you have 8 members in your clan at the time of roster lock and recruit 4 more before the war starts and those new 4 score first there scores will count along with four more for a total of 8 whose score counts , now that would leave 4 people that were already in your clan having there score not count.
The first 8 in your clan to score would have there score count while the other wouldn't regardless of if the joined after the roster lock since it is on the number of people whose score counts.