For Microsoft System Center Operations Manager 2007 R2 (SCOM) to be installed correctly, a number of roles and configuration items need to be in place. On a default installation of Windows Server 2008 R2, if you run the prerequisite checker, a number of components will show up missing even if the IIS and .NET roles are enabled. It’s cumbersome to diagnose the specific roles, though it is documented in the prerequisite checker and on TechNet.
You can use PowerShell to automate the complicated configuration steps. There is one supplemental download that should be installed manually, however. The ASP .NET AJAX 1.0 framework (which is a 1.5 MB download) needs to be installed manually before the roles configuration can be performed. Once the installation is complete, the server is ready for a PowerShell script to configure the prerequisites for a SCOM server.