Event admins may set a Roster Lock Date under the event Setup > Pricing & Modes > Team Registration settings:
If the Roster Lock Date is beyond the registration close date, then team admins can add a new player to their roster despite registration being closed.
If the Roster Lock Date is before the registration close date, then team admins cannot add a new player to their roster despite registration still being open.
The roster lock date only affects adding new players. Players that are incomplete after the roster lock date goes into effect are still able to complete their registrations.
Note: "Team Members" registration must be activated for the Roster Lock Date option to be activated.