Roo-buh-tru means "rude, but true". You can throw an insult at someone as long it's justified with truth.
"Dang girl, yo hair is tore up today."
"Ugh, roo-buh-tru!"
"So this chick at Chipotle put me on blast because my card declined when she rung up my burrito! Roo-buh-tru!