In romaji is it okosan or oko-san? I am reading the Japanese for Busy People book and I notice in the dictionary in the back some of the words ending in san use a hyphen: okyaku-san and some don't okosan Sometimes they use a hyphen after o- o-kashi and sometimes not okyaku-san Does anyone have any idea why they do this?

I don't think there is a "right way". There are many ways to use romaji and each with their own rules. In general, names like Takeda-san, Takahashi-san tend to use the hyphen while words like okasan, otosan, etc tend to not use them.

The hyphen after the o is probably used to indicate that the o is not part of the word itself but just a polite prefix. But to use it or not is also dependent on what kind of romaji rules you abide to.