Okay this might help some note 2 users here..
If you are facing a problem of screen rotation sometimes not working, then you have to reboot your phone, which of course is a doing which would cause detrimental effects by minimizing the life span of the phone.
I did some researching about this problem, and I found out that the best way to solve this problem, which in my case until now, a few days into it after performing this task still seems to work for me.
Here is it:

First you have to switch off your phone, remove battery cover, remove battery, remove sim card, and remove memory card. Basically remove everything, except the screws..

Then repeat the above steps, but in reverse. Switch it on and there you go, screen rotation would work like magic.
It seems that most note 2 users agreed that this is the method that works best for most people, and I am one of those users.

Hope this would help those users who faced this problem..