SQL Server role those things

Fixed server role Description
The sysadmin can perform any activity in SQL Server.
ServerAdmin can set server-wide configuration options to shut down the server.
Setupadmin can manage linked servers and startup processes.
Securityadmin can manage logins and create DATABASE permissions, and can also read error logs and change passwords.
Processadmin can manage processes that run in SQL Server.
DBCreator can create, change, and drop databases.
Diskadmin can manage disk files.
Bulkadmin can execute BULK INSERT statements.

Fixed database role Description
DB_Owner has full permissions in the database.
Db_accessadmin can add or remove user IDs.
Db_securityadmin can manage all permissions, object ownership, roles, and role memberships.
Db_ddladmin can emit the all DDL, but cannot issue a GRANT, REVOKE, or DENY statement.
Db_backupoperator can emit DBCC, CHECKPOINT, and BACKUP statements.
Db_datareader can select all the data in any user table in the database.
Db_datawriter can change all data in any user table in the database.
Db_denydatareader cannot select any data from any user tables in the database.
Db_denydatawriter cannot change any data in any user tables in the database.

Exception: "The user default database could not be opened. Login Failed "

Workaround:

You need to set up a user mapping for that user as an administrator for the default login database, as described in the user properties:

Exception: Denied SELECT permission on object ' extended_properties ' (Database ' Mssqlsystemresource ', schema ' sys ').

WORKAROUND: Do not select the database role marked on the way

SQL Server role those things