Role Description
sysadmin This role has ownership of SQL Server. This is similar to Domain Admins or the Administrator account in Windows.
serveradmin This role sets serverwide configuration options and can also shut down the server. This is similar to the Windows Power Users local group.
setupadmin There's no real counterpart in Windows to the following roles—except maybe using Group Policy Objects. This role can link to other SQL Servers and can change startup procedures for the server.
securityadmin This role creates logins and also has the CREATE DATABASE permission. It can also read error logs and manage passwords.
processadmin You may find this role useful to assign to developers. It allows an account to manage SQL Server processes. It can save you a phone call.
dbcreator This role can create, alter, and drop databases.
diskadmin If you're managing a large database server, this role allows an account to manage the disk files.
bulkadmin This role allows an account to insert large amounts of data into tables. You'll often see this role used in OPAL shops.

Table 1 Take the Role Roll Call.
Each role has different duties and capabilities attached to it.