remove all components from a board with oven/heater?
The solder used in for much of consumer electronics melts at temperatures of about 180°C. So temperature-wise there is no problem using a normal oven to do the job.
Even at 180°C components will unavoidably get damaged. Different components react to heat differently.
The first to suffer are typically connectors with plastic housings (e.g. to interface with a PC etc.). They are extremely difficult to remove without damaging the plastic. Other components tolerate heat better. The lifetime of aluminum electrolyte capacitors however is likely to be reduced by repeated heating. With ICs, there is less of a risk of classic thermal damage but rather due to mechanical stresses resulting from too fast heating or cooling. - On the whole however, components will not suffer too much if you don't keep them heated for more than a few minutes.
If you want to avoid using an oven for heating, you can fix the board horizontally in a vise and heat it from below with a heat-gun until the solder liquifies. Then take the board with pliers and tap it vertically on the table. The components will fall off quite easily.


Attention: with a heat-gun it is easy to over-heat the board or heating the board too rapidly. Solder in vias may be ejected outwards due to the rapid heating: wear eye-protection if you really want to do this.

Generally however it is not worth recovering components en masse from assys: What you recover will typically be proprietary chips you cannot really use, tiny smd capacitors too small to handle, and unmarked smd capacitors and inductors. - I propose you only remove those components that you really want/need.