When building, I notice that the skybox influences the color of the light that leaks through parts. How do I fix this?
Placing a large block over the build does fix this problem, but it makes the view outside the window unattractive.
Using a black skybox does fix the problem, but that messes with the lighting.
Did you also maybe try to use a white skybox cause idk what to do else this is just a suggestion idk if it works.
A white skybox wouldn’t fix the issue either because that would make the view outside unattractive. 
The part on top is definitely too thin, I say extrude that a lot or put a large barrier on top of it.
By extruding do you mean resizing the part longer?
Longer and taller or either one of the two, whatever solves your issue.
It extends the part or vertex of it
What are your values inside of game.Lightng? Like what settings do you have in there such as ambient, etc?
Roblox issue sadly, not much we can do.
Have you considered turning off Shadows??
That didn’t fix anything. 
how about placing two parts together with a little bit of space between them
Did you try putting a block over that certain area instead of just putting a large block on the top?
Try making the top part of the roof bigger
Resize it to were it matches up to the green part
Not sure how exactly this should look like though, if someone could provide a visual representation that would be great.
I’m assuming that you’re using future lighting,
Instead of putting the pointlights directly in the ceiling lamps, you should make an invisible placeholder part slightly below the lamp itself to illuminate the ceiling and drown out the skybox light.
Since I’m terrible at explaining things here’s an illustration:
Since future lighting is a bit wonky and putting a point light directly next to a part doesn’t light up the surface it’s right next to (annoying), you have to compensate by placing the point light farther so that surface can be illuminated.
If you’re not planning on going outside and all these other methods fail…you could also try putting in a separate room meant to absorb the light that players won’t see in-game.
Example:
Turn ColorShiftTop 0, 0, 0 OutDoorAmbient 0,0,0 and ColorShiftBottom 0,0,0 in the lighting properties. and make sure the roof is not transparent! if that don’t work it could be a bug on Roblox end.
