At the A.G.M. in June 2019 clubs voted to use Roll-On Roll-Off substitutes throughout the League and in all Cup competitions controlled by the league.
Below are details taken from Rule 20 (F) which explain the procedure.
A Club may at its discretion and in accordance with the Laws of the Game use substitute Players in any Competition Match. A Club may use up to 5 from 5 substitute Players in a Competition Match.
A player who has been substituted himself becomes a substitute and may replace a player at any time subject to the substitution being carried out in accordance with Law 3 of the Laws of Association Football.
The referee shall be informed of the names of the substitute Players not later than 15 minutes before the start of the Competition Match and a Player not so named may not take part in that Competition Match.
A Player who has been named as a substitute before the start of the Competition Match but does not actually play in that game shall not be considered to have been a Player in that Competition Match within the meaning of Rule 18 of this Competition.