I'm doing an audit of that title, Norwegian edition, since it's a copy of imdb. Cast entries entered as: Name - Role(as name name) in the credit field, and castnames (scenes deleted) etc etc. However I can't find out all the roles in the openingcredits, that's 21 names. All the others are listed with roles in end credits. I have used the role names as credited before, and checked against http://movies.tvguide.com/helter-skelter/cast/137484, don't know if that's a reliable source though. Also checked against other profiles, so it seems to be correct as it is, but I'm missing rolenames for two persons now, and they are Keith Szarabajka and John Pleshette. The rest of the cast are listed in end credits, so I really need the rolenames for those two persons. And also what is a reliable source to get rolenames from.

From the Contrubution Rules:

"If an actor is credited by name but does not have an associated role, you may use the film itself, or another source to identify the role. However, mass copy from a third party commercial database which violates their stated usage license is not allowed. In each case, list Actor’s names and roles (when given) exactly as they are in the credits and in exactly the same order credited."

You can use a third party source. I would suggest using two or three in order to ensure the accuracy of the information. Quote the sources in your contribution notes.