I can't imagine any meaning of "in the room of" other than "in the place of; instead of."

The OED has it from the 16th century. It is still in use in Great Britain.

I disagree with Gilchrist about "fountain of snow." What makes her think that a striking and perfectly understandable simile must have been the result of mishearing something far less good, rather than pure inspiration? If mishearing was involved, an earlier "mountain of snow" would undoubtedly be more plausible. But "fountain," IMO, is better still.

Without earlier texts from the identical lineage, no proof seems possible in any direction.