"playing different roles" is kind of nebulous, though - and especially historically, it doesn't really mesh with what has been considered an RPG. Depending on your strictness of definition, quite a bit more than "a few oddities" among the RPG classics would not fit this definition, on the other end it would encompass a ton of non-linear P&C/VN/Interactive fiction in general.

I know that the moniker has it's issues when taking it literally, but doing so too strictly makes the term almost meaningless when discussing genres. (..."even more meaningless", some may argue. ;) )