Comedy replacement for "uh oh", Scooby Doo style.
Guy 1: OH SHIT MY HOUSE BURNED DOWN!
Guy 2: RUH ROH!ahhahaha
Scooby Doo's comedic mispronunciation of "Uh Oh", it is also a play on potentially dire situations, usually starting with a minor event that could escalate into something huge.
North Korea just shelled a South Korean island? Ruh Roh!
There is a small leak from the dam? Ruh Roh!