Can i have the desktop (case) in one room and screen keyboard mouse in another?

Yes, it's possible.  It will be a little expensive to do this.  Also, it's not portable; you'll be tied to one location.

You'll need a hardwire Ethernet cable from the desktop to the remote location.  This operation does not work well over wireless; the video is constant and eats up the wireless bandwidth.  Also note that most Ethernet KVMs are VGA only, not HDMI; you'll be restricted to a VGA monitor and standard VGA modes.  Expect "some" video quality degradation.

Purchase an Ethernet KVM, run the cable between the two locations.  Plug the computer's keyboard, video and mouse connectors into the local KVM.  Plug the keyboard, video and mouse into the remote KVM.

Example KVM-over-IP (Lantronix Spider):  http://www.lantronix.com/it-management/kvm-over-ip/

Hi schas123,

desktop (case) in one room and screen keyboard mouse in another : I think it is not a good Idea.

My suggestion  to Buy a laptop with wireless keyboard and mouse or   Surface Pro 3 .

You mean use RDC like John Hurst suggested or something else?

A Grade advice, thank you.

@schas123  - You are very welcome and I was happy to help.

If you prefer to maintain your desktop environment in other rooms a small thin client might not be much trouble to move around. Something with built in wireless perhaps you could set up remotely. http://www8.hp.com/us/en/thin-clients/t510.html