Toyota Repair: Vibration when Engine is cold, clutch pressure plate, alignment problems

Question
Vehicle : Toyota Corolla 1.6GLS (1992) FWD

I feel a vibration on the steering wheel when my
car is idling. The front Bumper vibrates. There is a rolling sound coming from under the car whilst the vehicle is idling and is especially noticable when the engine is cold.

1) Ive had my exhaust checked and is O.K
2) The front mountings have been replaced. I still have the same problem
3) The vibration has started since Ive had my clutch/pressure plate & Bearing Replaced. The Gearbox, front and back mountings and crossmember was removed to replace the clutch.

When I loosen my front mounting from the cross member the vibration stops. The car idles smoothly.

Please Help  

Answer
It's obvious that there is a motor mount problem or a mount misalignment, check all the mounts to make sure that there is no metal to metal contact between the mount brackets and the frame or crossmember, if the car has ever been in a front end collision it could also cause motor mount alignment problems, try loosening the front mount and move the engine up or down and tighten it and see which direction of movement helps, once you find the position of the mount where the vibration stops secure it.
Check everything again, one of the motor mounts is making contact with the body or frame of the car, this is the only thing which will cause a vibration like this, it could also be an exhaust part making contact with the body but you said you had it checked and it was ok.