In this Oct. 30, 1986 file photo, talk show host Joan Rivers, right, talks with guest, first lady Nancy Reagan, during her appearance on "The Late Show Starring Joan Rivers, " on Fox TV. The role of female talk-show hosts in late-night TV network history, all 50-plus years of it, can be summed up in two words: Joan Rivers. It takes just another two - Arsenio Hall - to do the same for minorities. There's no indication that's going to change in the latest round of musical chairs involving "Tonight" and "Late Night."