Steve Spencer's Blog

When using the following code from a worker role the trace information shows that there are one worker role instance and zero web role instances

public override void Run()
{
    while (true)
    {
        Thread.Sleep(10000);
        Trace.WriteLine(string.Format("WorkerRole Instances {0}",
            RoleEnvironment.Roles["WorkerRole1"].Instances.Count),
            "Information");

        Trace.WriteLine(string.Format("WebRole Instances {0}", 
            RoleEnvironment.Roles["WebRole1"].Instances.Count), 
            "Information");                
    }
}

This is because an internal endpoint is required on the role in order for the role environment to be able to retrieve the instance count. So add a new end point to the webrole and set it as internal. Running the code again, then shows both roles with 1 instance running.

See the Role.Instances MSDN topic:

http://msdn.microsoft.com/en-us/library/microsoft.windowsazure.serviceruntime.role.instances.aspx