So the idea is to have my main characters wake up from cryo with no idea of how long they were in it and stumble upon a room full of bodies completely decayed to bone and however long they were in cryo the rest of the station lost oxygen after the people in the room died,the room is sealed off to the rest of the space station and life support was off so how long would itve taken for them to become bone?
With no oxygen present, a very long time.
Decomposition is a process where organic material degrades, and can do this through biotic or abiotic means. (Either bacteria break it down, or it breaks down naturally.)
Since there's no oxygen in this scenario, and it is in space with no direct sunlight it's wayy too cold for bacteria to break anything in the bodies down. So that's the biotic method out.
How about the abiotic method? Well first off the bodies would all dry out like a mummy, since it's so cold that water in their cells will freeze. If the room is open and sunlight occasionally comes in, it may sublimate the ice and crumble the bodies slowly down to dust and bones over hundreds of years. Exposure to solar winds and high speed cosmic particles that are natural in space will eventually blow away the dust, leaving just the bones behind. If not, then the bodies will likely remain as freeze-dried mummies. At this point it's not really decomposition though.
As you said the room is sealed though, so it's just a pure vacuum with no life support. In this case I'm afraid the bodies will likely be perfectly preserved as freeze-dried mummies, like what has happened to the countless bog bodies or people found mummified in mountain top caves, only far better preserved.
If there's a way to have life support fail because this sealed off room was exposed to space directly (maybe something hit it or broke the walls), then we can bring in high speed cosmic particles that can help dust the flesh off the bones and hopefully get you your room full of skeletons!
So in this case, it will likely take a very long time, with you getting some creative freedom to handwave a large number of years or centuries, or even millennia, to have passed by. Hope this helps!
Edit: This answer from another question on this site may help give some more insight too!