This was overheard in a disability hearing. It is a nice mashup of “through the roof” (to rise to a very high level) and “out of this world” (extraordinary). The word “roof” seems to be the cause of a lot of idiom jumbles. Check out other “roof malaphors” in the search engine. One I vividly recall is “the shit hit the roof”. https://malaphors.com/2014/09/20/the-shit-hit-the-roof/. A big thanks to Sam Edelmann for sharing this one.
If you liked this one, you’ll love my book on malaphors, “He Smokes Like a Fish and other Malaphors”, available on Amazon. It’s out of the roof!