Room temp is the ambient (surrounding) temp, isn't it?I have until now thought that it is the room temperature that matters, not the ambient temperature.
The actual temp of the beer (in the fermenter) is important. But it's difficult keeping a thermometer probe in the beer, unless one uses a thermowell.
Therefore we usually measure the beer's temp by taping or strapping the temp probe, placed underneath a piece of 1/4-1/2" thick, dense packing foam against the side of the fermenter in the middle where the beer is. The foam prevents the probe from reading the ambient temp too much.