Looking back at this post, if you only have small and big rooms, and that’s all you need to distinguish between, you could just put something in the level name, to tell them apart.
Then, depending on the level name, you know how far to offset it when you load.
Another way would be an array of level references, and an array of level sizes. When you choose index 7 ( say ) randomly from the level array, you just grab index 7 from the size array and you know how far to offset.
( I’ll leave you alone now … 
)