Follow these steps -
- Install the feature using a startup task:
PKGMGR.EXE /iu:IIS-ApplicationInit
- Configure your site in IIS (startMode and preloadEnabled):
public class WebRole : RoleEntryPoint
{
    public override void Run()
    {
        using (var serverManager = new ServerManager())
        {
            var mainSite = serverManager.Sites[RoleEnvironment.CurrentRoleInstance.Id + "_Web"];
            var mainApplication = mainSite.Applications["/"];
            mainApplication["preloadEnabled"] = true;
            var mainApplicationPool = serverManager.ApplicationPools[mainApplication.ApplicationPoolName];
            mainApplicationPool["startMode"] = "AlwaysRunning";
            serverManager.CommitChanges();
        }
        base.Run();
    }
    public override bool OnStart()
    {
        // For information on handling configuration changes
        // see the MSDN topic at http://go.microsoft.com/fwlink/?LinkId=166357.
        return base.OnStart();
    }
}