I do not own this machine, but have brought other roller processors back to life.

The heater should be able to be tested while the unit is powered down with an ohm meter across it's terminals. It should have a resistance of a few hundred ohms.

I other weak point can be the control temp sensor.

I am not aware of anyone distributing parts for Durst in North America, although Omega Satter once did I believe.
I am not sure who inherited the Durst parts chain on your side of the ocean.