How likely is it that there is someone knowledgeable about piloting in a flight control room?
The answer depends a lot on the type of plane being flow.  While plenty of air traffic controllers are also pilots on the side, it is highly unlikely that anyone on duty at the time would happen to have a type rating in a large complex turbine aircraft, and/or enough knowledge to talk through checklists.  They may be able to offer very generic advice such as "See the handle that is shaped like a wheel?  Push it down and that will lower the landing gear."

For simpler GA aircraft they might offer some basic assistance on how to control the aircraft, slow down, deploy flaps, etc. but there is a lot of muscle memory and technique honed by hours of practice needed to perform a "good" landing.  Just explaining the exact steps to take over the radio isn't going to be enough, there is a lot more to it.  

Think about the first time you drove a car with a manual transmission:  Did the person telling you to push in the clutch, shift gears, then let it out smoothly while adding gas help you to do it smoothly, without stalling the engine, jerking, or racing the engine?  Probably not!

About the best they could probably hope for is to help the non-pilot maneuver into a safe airspeed envelope to survive a controlled crash landing at the airfield where emergency services will be on hand to provide immediate help.