The largest room is not always the easiest place to record a clear conversation. Hard walls and bare surfaces can make speech sound distant. A smaller furnished room may work better, but only a recording will tell you how the microphone hears it.
Compare two real options
Use the same microphone, gain and speaker position in each room. Record a normal sentence, a louder sentence and ten seconds of silence. Include a few words with clear endings so you can hear whether the room sound continues after the voice stops.
Listen for two separate things. Echo follows the speech. Steady noise, such as ventilation, continues while nobody speaks. A room can be good at one and poor at the other. Write down both rather than giving the room one vague quality score.
Try moving away from a bare wall or a large window. Soft furnishings can help, but keep ventilation, exits and equipment safe. Do not create an uncomfortable sealed space for a long recording.
Test the interview conditions
If the room will be used during the day, test it at a similar time. A quiet late-night sample will not reveal nearby work, traffic or other regular activity. Check whether a door needs to remain open and whether a laptop fan becomes louder after several minutes.
Choose the room that gives the clearest repeatable voice, then keep its setup simple. Take a setup photo for your own notes. You can improve many small editing problems later; removing strong room echo from every spoken word is a much harder starting point.