IMHO, no because 室内 functions as an adjective not a preposition. Examples: [context.reverso.net]
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student456
I made a typo in my original message, I asked can those characters "even" mean in a room, but naturally I meant: can they EVER mean in a/the room.
So I repeat the question: if we just think of the characters 室内, can they EVER, in any case, dialect, poor language, mean in a/the room?