In a good team, the manager is the boss.

What this means is that they run things and are the first port of call for parents and others wanting to contact the team.

A good manager will do evrything they can to take work off the coach so that the coach can concentrate on preparing the players for the games.

This can include (but is not limited to)...

• Drawing up the roster for laundry, oranges, treats and whatever else and ensuring parents know when it is their turn.
• Organising communication between the coach and parents about training.
• Informing the team where and when the games are.
• Working with the coach on sideline rotation and ensuring players are taken on and off at the proper time (the coach should be totally focused on the game - not watching a stopwatch and having kids tugging at their sleeves).
• Keeping track of who is in what position.
• Keeping track of team stats - who has scored, who has saved, who has set up shots
  
• Keeping track of who has won player of the day and laiasing with the coach over who gets what awards.
• Checking things with the other team.

Essentially, the more time the coach can focus on the kids the better - everything the manager can do to relieve the coach of small tasks that take them away from that, they should.
They do not have to operate alone.  They can recuit other parents for specific tasks like tracking team stats.