There are a few things that come into play when colonist build roofs.
Rimworld built room but roof not working.
The roof is supported far as 6 tiles.
I personally think it should work the other way but there you have it.
Items purchased from a trader will be dropped within range of a beacon if unroofed otherwise they will be dropped as close to the beacon as possible avoiding.
If there is any tile with is not in that range the roof will not be builded or that tile will not be builded.
A roof will not be fully built in a room that is more then 11 blocks between two parallel sides.
To build a roof outdoors a build roof area must first be drawn.
Indoor roofs are automatically built by builders.
That means the 7th tile must be supprted.
You can select one of your colonists and then right click inside the room and prioritize building roof should be an option.
If the room is open in some area or the door gets jammed open all the cold air escapes.
And that is for everywhere from every side.
1 does the roof have support.
Trade beacons will work under a roof.
The no roof tool highlights areas that should be considered outside.
Larger roofed areas can be built with the use of interior walls as pillars.
Areas can be designated to have a roof or not have a roof by drawing either a build roof area or remove roof area.
Solid walls and separate rooms will break the area of influence of a trade beacon however support columns for larger rooms don t block its effect.
As long as there is no other work to be done in there with a higher priority the colonist will finish building the roof.
If you removed 2 entire walls and the corner between those two sides last then that roof was too far away from any other supports.
A roof collapses if there s no support rock wall within 6 squares of the tile.
What the other people said is part of it as well your room is 13 wide which is 0 2 too far in supported so you have a hole in the ceiling in the middle of the large room.
Once he she is inside the room forbid the door so the colonist can t leave.
Make sure you click on the ac and set it to 10c for freezing or more 0c for refridgeration.
Make a hole in your room and then close it to trigger the roof build.
Make sure the blue side is facing the room and the red side is facing out make sure the room is enclosed and has a door the bigger the room the more ac s you need.