French for "Let the good times roll." It's a common expression in Louisiana (not in France), though it's almost always spelled incorrectly. This is the one and only correct spelling of the expression, in either Cajun French or Parisian French. Sadly, even reputable institutions like the Audubon Zoo and the New Orleans Ironman 70.3 use variations of incorrect phonetic spellings they find online.
Free beer and live music? Laissez les bons temps rouler!