Additional Info: No exits or windows in room.
The temperature of the room will increase. The 1st Law of Thermodynamics tells us that energy cannot be created or destroyed, only getting transferred from one state to another.
When you open the refrigerator, or even with the refrigerator door closed, in a perfectly sealed room with no heat loss, there will be an increase in the room temperature.
A refrigerator uses mechanical components to extract heat out of the surrounding air. As such, since these mechanical components use electrical power, there’s always the generation of heat that these devices produce! This is why in a room with no heat loss, the room increases in temperature as these devices are actively generating heat to reach the internal temperatures of the refrigerator.
In the case of with the door open, the surrounding air encompasses the entire room and thus the system works harder to meet the desired temperature. In effect, the mechanical components (compressor, motor) will increase the room temperature from heat loss.