E-R Model to Rails

Hi guys,

I'm helping some friends develop a web-based roster management system
for a league they play in. We chose Rails over php or py because of the
DB facilitities and mapping that RoR offers. Any help will be greatly
appreciated.

I've draw an E-R diagram of the model. However, I'm having a hard time
implementing the design in Rails. It goes something like this:

League has_many teams
Team has one roster AND belongs to one League.
Roster has many players and belongs to one team.
Player belong to one team.

On top of that we have to add the ability for the league admin to do
CRUD on all the rosters/players. And team cap's will access to only his
or her team's roster to do CRUD (unless a manually selected drop/add
period has expired).

I believe my model is almost right (something smells though)...however,
I'm at a loss insofar as how to go about the admin/CRUD part of it.
Again...any help is tremendously appreciated.