As a Team manager, you can update your teammates attendance if you know whether or not they will be coming.
First, select the event in questions from your team's Events tab and then scroll down to the team roster.
Now, simply tap In or Out beside the corresponding player to set their status.
Players will now be ordered by attendance, with those attending at the top, those not attending below that, and those who have not yet responded at the bottom.
You can also send out invites to specific players or spares prior to the normal invite window if you need to by tapping the red "Invite" option.
If a player has a green ✓ that means they have been sent and received their invitation. The red X, with the invite button below, means they have not been sent an invitation. A red X without the invite button means they have been invited but have not received their invitation (players who are not receiving their invitation have either not verified their email address in RosterBot or have turned off their Team Notifications via their Profile page).