The deadline only applies for the visiting team. The NHL has a rule where the visiting team must submit their lineup first so that the home team can view it and make the appropriate adjustments. SimLeague Hockey honors that rule by imposing a deadline for the visiting teams. If your next game is on the road, you have until 11:59am ET to set your lineup if the next game is a PM game. If it's an AM game, you have until 11:59pm ET to set your final lineup. Once the deadline passes, your game roster, lines and pairs will be locked until the game plays.
If you are the home team, you have up until the game is simulated to set your lineup (between 2:15 and 2:45 AM/PM).
In order to make it fair for all teams, the waiver wire will be locked for both home and away teams during the time that visiting teams' rosters are locked.