When you add the Web Server role in Windows Server 2008 you will end up with a wealth of options. What you could do instead is to run the installation from a command prompt with all the options pre-configured. A very convenient way of installing IIS 7 with all the right stuff you need.

This command will get you a default configuration for running EPiServer CMS 5 R2.

start /w pkgmgr /iu:IIS-WebServerRole;IIS-WebServer;IIS-CommonHttpFeatures;IIS-StaticContent;IIS-DefaultDocument;IIS-HttpErrors;IIS-HttpRedirect;IIS-ApplicationDevelopment;IIS-ASPNET;IIS-NetFxExtensibility;IIS-ISAPIExtensions;IIS-ISAPIFilter;IIS-HealthAndDiagnostics;IIS-HttpLogging;IIS-RequestMonitor;IIS-HttpTracing;IIS-Security;IIS-BasicAuthentication;IIS-WindowsAuthentication;IIS-URLAuthorization;IIS-RequestFiltering;IIS-Performance;IIS-HttpCompressionStatic;IIS-WebServerManagementTools;IIS-ManagementConsole;IIS-ManagementScriptingTools;WAS-WindowsActivationService;WAS-ProcessModel;WAS-NetFxEnvironment;WAS-ConfigurationAPI

You could do some additional tweaking here like removing Windows and Basic Authentication if you won't be using them, just remove IIS-BasicAuthentication and IIS-WindowsAuthentication from the command above or click on Remove Role Services in the Server Manager.