Loosely based off of how often Lindsay posts about her vivid dreams/nightmares - I like to imagine that Ruby has the same issue.
Given her wild imagination, Ruby probably has a lot of really intense dreams. Some of them good and some of them not. Yang is accustomed to it, she’s had many nights where she wakes Ruby up when she starts talking or yelling in her sleep.
It was a harder adjustment for the dorm room though, when Blake first heard Ruby yelling “WHERE IS SHE?!” it was pretty scary. Especially since she only really knew Ruby as a bubbly and bouncy kid.
Weiss hated it at first, if only because the one time she woke up and tried to help it was after Ruby had a really bad nightmare and started crying and talking about her mom and Weiss was completely unequipped to help. It made her feel bad, like failing a test. How could she be the best partner ever if she couldn’t make Ruby feel better?
So she eventually asked Yang for some advice and when she said she wanted to help deal with it, on the rare occasions it came up, Yang was surprised but grateful. Blake wanted in on it too, for team unity and all that. Not because she cared - she didn’t. Of course not…not Blake Belladonna….nahh.
Eventually, they worked out a system and if Ruby started talking in her sleep, first one to hear it was on Ruby Duty.
Blake would usually hear it first, but if Weiss happened to as well it was Weiss’ turn. For the really bad ones, they’d bring in Yang and Yang would sit up on Ruby’s bunk until she calmed down and both Weiss and Blake would usually stay up, pretending to be asleep, waiting for Yang to come down meaning Ruby had fallen back asleep.
It’s not anything any of them talked about, and it didn’t happen very often, but Ruby’s dreams were something all of them became very aware of and adjusted to.
When Beacon fell, Ruby didn’t have anyone there to help her through the bad ones. It took a toll on her for a while because she struggled to fall asleep. Once she hit the road with Jaune, Nora and Ren - it was something she knew would happen and hoped she could handle. She was trying to convince herself every day that she was old enough to take care of herself. She didn’t need a bed buddy to help her through a bad dream.
Then a bad one hit her during a night camping in the forest. It wasn’t her mother or a Grimm attack - it was watching Penny be torn to pieces. It shook her, badly - to the point that she woke up screaming and scared the hell out of her new team.
With no way to keep it to herself, Ruby told them all about her dreams and how they’ve always been something she’s dealt with. About how after Beacon fell, they were even worse and more like flashbacks than nightmares - tormenting her.
That’s when Nora started sleeping a little closer and Ren started helping Ruby clear her mind before it was time to go to bed with breathing exercises and good stretching routines to help her relax. Jaune would make a note to tell dumb jokes he’d heard or tell Ruby about all the silly things he collected as a kid.
The nightmares lessened and Ruby found herself sleeping better. Which made it all the easier to help Jaune when she found out he wasn’t sleeping well either