A full size roulette wheel in modern casinos is 80cm, or 32 inches. Because there are only several wheel manufacturers, they are much the same dimensions with any of the full size professional wheels.
There are various parts of the roulette wheel, with the most common being wood. Wood is usually the foundation of the wheel, although it usually has an aluminium bowl inside which is highly resistant to shrinkage or variations.
Some roulette wheels are made of a hardened type of plastic called ABS. These are usually completely black. The wheel is made of wood are coated in a quite tough epoxy. It is quite similar to a product called Areldite that you can purchase from your local hardware store.
The ABS wheels are created from a mold, whereas the wooden wheels are carved out by a machine. The process is quite entertaining to watch. You see a near worthless block of wood being carved out into what will becone a casino roulette wheel worth around $10,000. Add a metal bowl and metal deflectors, and a center spinning rotor, and coat it with fine epoxy. Then you have a mechanical device that many losing players will want to swear at when the ball comes to rest.