At long last, I have canon proof of the rooms for Captain Kirk, Officer Spock, and Doctor McCoy. Maybe this can help clear some things up for y'all, if you're interested, or maybe you want to learn this particular, dug-in-deep piece. But I have finally found evidence of where those rooms are. And for those who believe that Kirk and Spock share a bathroom: I'm sorry, but no.

Kirk: 3F 121

I found this in the episode 'Journey to Babel' as he and McCoy exit at the very beginning. I zoomed in on the plate number and it read that.

Spock: 3F 125

I noticed this in 'Amok Time' when Nurse Chapel goes to bring him plomeek soup. Sure enough, the plate number read 125. Sorry, but 121 and 125 aren't likely to be next to each other to share a bathroom.

McCoy: 3F 127

This is the only room number the show zooms in on in 'The Man Trap'. All the others took serious digging, but hey, I'm obsessed with canon.

Also, just as a bonus if you're curious, Yeoman Janice Rand's quarters are 3C 46; shown in 'The Enemy Within'.

I suppose it's possible that McCoy and Spock share a bathroom, if even numbers are on the other side of the hall. I shall have to find proof of this, though (plus that's a weird thought).

Well, there you have it, folks! If you want to use the information in your stories, go ahead! If I come across any other crewmembers' room numbers, I will post them as well. Seriously, I love canon way too much.