The roof separation was investigated in a coal mine as part of the site characterization of roof strata deterioration in a longwall roadway. The separation of laminated,weak roof strata was initially characterized as the maximum separation, effect of geological setting on separation and the effect of mining activities (heading development,time-dependent and longwall extraction) on separation. Then the separation process was studied, so as to answer the questions of: when the separation occurs; where the separation is located and what geological setting it relates to; how large of the separation is; and how the separation propagates.