There was an error processing your request. Registered role required

I am getting a wierd error.

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Registered role required
Environment Information eSpaceVer: 91 (Id=4546, PubId=5592, CompiledWith=
RequestUrl: (Method: GET)
AppDomain: /LM/W3SVC/1/ROOT/NotificationUI-243-130946574538517396
FilePath: C:\...\PS\running\NotificationUI.322471550\CohortSubscription.aspx
Locale: en-US
DateFormat: yyyy-MM-dd
PID: 4324 ('w3wp', Started='12/3/2015 1:05:43 AM', Priv=761Mb, Virt=18359Mb)
TID: 79
Thread Name: 
.NET: 4.0.30319.34209
Registered role required
   at ssNotificationUI.Flows.FlowMainFlow.ScrnCohortSubscription.Preparation(HeContext heContext)
   at ssNotificationUI.Flows.FlowMainFlow.ScrnCohortSubscription.Page_Load(Object sender, EventArgs e)
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

Can anyone help me in here?
What is weird about it? As the error says, you need to be at least registered. Apparently you weren't logged in, then tried to access a page that needs at least a Registered user.

EDIT: Btw, why isn't this in the tech forum?

But, when I hit the page this should redirect me to the login page. But it wasn't taking me there instead throughing that error. 

When I give anonymous access then I was able to access the page. 

If you don't get redirected to the login page, you're neither explicitly handling this yourself, nor using a theme that has exception handling.

EDIT: P.S. If you expect to be redirected, why not put that in your first post? Instead, you said it was "weird". You can better describe what you think is weird. It's easier to help you then.
May be that could be a reason as I am using SILK UI dublin template theme. 
I'm not sure whether that has login stuff out of the box.
Now, Even though I have revoked anonymous access from the pages, I am still able to access the page. This time I am not getting any error. 

It's strange. 
See, screenshots 

I don't see any users associated with my application under Users app neither I am seeing application name under users role dropdown.