There is no such concept as "the other entities being saved that my AdapterProvider is not handling?"
When you use a custom AdapterProvider for, let us say, the Employee table, then that means that all Update, Insert, Modify, and Delete operations for the Employee table are being handled by your Adapter Provider
In most cases the default DataAdapter used internally by DevForce is sufficient for all business objects. The RdbAdapterProvider creates a provider-specific DataAdapter appropriate to the connection, and builds the SelectCommand, UpdateCommand, InsertCommand and DeleteCommand needed for the EntityTable.
A typical reason to implement a custom AdapterProvider is to call your own stored procedures when updating, inserting and deleting data. When implementing this interface, you will construct and initialize a DataAdapter with the UpdateCommand, InsertCommand and DeleteCommand which the framework will then use for all data modifications to the underlying data source. You will also provide the Refetch logic to re-query the data source after modified rows have been saved.