Newbie Questions On Schemas, Roles, Users & Logins

Sql 2005
I want to grate execute permissions on my stored procedures to a role. While creating the role, it asks for "schemas owned by this role".
To me, the schema is merely a namespace that allows you to group objects, but arent schemas such as db_datawriter roles that are central to the db and only admin type users should have ownership of these, correct ?

In a nutshell, I want to:
create a new role and assign a user to that role
with a stored procedure, grant execute permissions to this role

I was confused by the sql 2005 dialog that asks me to take ownership of roles such as db_datawriter, db_datareader etc, wouldnt that mess up other things with the database ?

help ...

I think its time I review all of the above items
role
user
login
schema