Best way to render a list of rooms

Hi! I made a floor plan random generator in Java, so I get a list of rooms, corridors, etc. Now I put the code in Unity and everything works fine but I wonder the best way to spawn rooms and render them. Cause I want to darken everything but the player actual room I mean:

¿Should I create everything (walls, floors, room objects...) and render it, and then darken everything but the actual room? Should I create everything invisible? (and make it visible and invisible again at runtime)

I have another problem: in my plans I didn't include the gap between rooms (and don't want to) but I want to render the rooms with visible walls (Like 2d Zeldas or The Binding of Isaac) that's why I want everything dark (The rooms aren't just a rectangle) any idea?

Thanks!