Many older cues develop a roll over the years, and most occur at the A joint as previously mentioned. Simply replacing the handle fixes the problem. The compound taper, if you are simply rolling the cue flat on the table, will make it seem like it is warped. I would do as suggested and take the cues to a cuemaker/repair person and have them spin the cues on a lathe. They will be able to tell quickly if the cues are straight.