create subtitles track by automatic timing of existing text
If you select your clip and go to the Clip menu, then choose Analyse Content, Premiere will attempt to identify speakers and even attempt to dictate what is being said.  You can assist this analysis by providing a script file to it by adding either an Adobe Story Script file or a TXT file to the Reference Script option.  I don't have any experience with how well this feature works, but it's certainly worth a shot if you already have an accurate script file to try it with.