출처 : http://worlds.lolesports.com/en_US/worlds/articles/2015-world-championship-rules

많은 분들이 궁금해하시길래.. 공홈에서 긁어 왔습니다.

Roster Requirements (Section 3.2) 

- 선수 로스터 / 롤드컵 공식 규정 3조 2항에 해당하는 내용

As with the 2015 MSI ruleset, all teams are required to bring one substitute in case of an emergency in which a player is unable to play.

- 지난 MSI 2015와 같이, 모든 팀은 교체 선수를 반드시 1명 보유해야 합니다.

We have this policy in place so that competitive play can continue without a forfeit in an emergency/unforeseen circumstances.

- 예측할 수 없는 상황 및 비상시에 대회가 정상적으로 진행될 수 있도록 하기 위한 부분입니다.

Teams with multiple substitutes will only be allowed to use one at Worlds.

- 다수의 교체 선수를 보유하고 있는 팀이라고 할지라도 롤드컵에서는 1명의 교체 선수만 보유할 수 있습니다.

This policy is designed to be a middle ground solution for participating regions where substitutes are used for a backup plan and regions where substitutes can be used as a strategic advantage -

- 이 규정의 이유는, 교체선수를 전략적으로 활용할 수 있는 지역과(strategic advantage)

교체 선수를 백업 선수로만 활용할 수 있는 지역(backup plan)들이 있으며.

그 지역들의 차이를 감안해서 결정되었습니다.

ensuring that everyone has a fallback plan, but teams with deeper sub benches aren’t at an automatic advantage.

- 단순 하게는 대비책 정도로만 느낄 수 있으나(fallback plan)

p.s  3조 2항의 상세 내용은 아래와 같습니다.

3.2 Roster Requirements 
Each team is required to maintain, at all times during the WCE, five players in the starting lineup (“Starters”), and one substitute player (“Reserve”) (collectively, the “Active Roster”) as well as an official coach. The Active Roster is considered locked as of September 8th, 2015, at 11:59am PDT. The Active Roster that was submitted to or known by WCE officials on this date will be considered the eligible Active Roster for the WCE. This roster lock will not supersede regional roster locks that may have occurred prior to this date. In the absence of a regional roster lock, teams will not be able to add any new players to their roster after their last regional competition preceding the WCE. 
In the case of an emergency, a team may add a substitute after this deadline, however, the substitute added must not have been on any other professional roster on September 8th and must have been eligible to be on a professional roster on September 8th. All Starters must have a written contract with the team they are playing for.