And I'm guessing there is no mapping for list styles?
You can select the stylesheet in the Project Settings dialog box. In RH11 it was File > Project Settings, but I'm not sure how to get to it in RH2015. Hopefully the RH11 details give you enough to figure out where to look.
Also, read Peter's guide to importing.
There is no mapping for single level lists but you can map multi level lists. There is no rule that you cannot use just the first level of a multi level list so that it is technically a multi level list but is used as a single level list.
See www.grainge.org for RoboHelp and Authoring tips
Thanks - I bit the bullet and just re-did the lists in RH. Easier than constant faffying with Word.