The Server Roles page lists all possible roles that can be assigned to the new login. The following options are available:
bulkadmin
- Members of the bulkadmin fixed server role can run the BULK INSERT statement.
dbcreator
- Members of the dbcreator fixed server role can create, alter, drop, and restore any database.
diskadmin
- Members of the diskadmin fixed server role can manage disk files.
processadmin
- Members of the processadmin fixed server role can terminate processes running in an instance of the Database Engine.
public
- All SQL Server users, groups, and roles belong to the public fixed server role by default.
securityadmin
- Members of the securityadmin fixed server role manage logins and their properties. They can GRANT, DENY, and REVOKE server-level permissions. They can also GRANT, DENY, and REVOKE database-level permissions. Additionally, they can reset passwords for SQL Server logins.
serveradmin
- Members of the serveradmin fixed server role can change server-wide configuration options and shut down the server.
setupadmin
- Members of the setupadmin fixed server role can add and remove linked servers, and they can execute some system stored procedures.
sysadmin
- Members of the sysadmin fixed server role can perform any activity in the Database Engine.
Reference: https://docs.microsoft.com/en-us/sql/relational-databases/security/authentication-access/create-a-login?view=sql-server-ver15
