Havas have defined that a Meaningful Brand is one that makes a Contribution to improving the quality of people's lives (via a number of defined Personal and Collective Outcomes) and one to which people show Attachment - they would care if the brand were to disappear.
I don't think having a role is under dispute, but I do wonder whose job it should be to define that role. Have you ever tried to define a brand's role? It's not an easy job, and you tend to keep coming back to a rather fuzzy area where the brand is a helper/enabler/facilitator/deliverer in or of the brand's benefit or some other aspect of its positioning. Or else you get into the relationship metaphors and the brand is a friend, or a chum, or a buddy, or even an ally - but invariably with the adjective "helpful" plonked in front. Or you might simply state that your brand's role is to stand on a pedestal and be an Icon of whatever your one-word equity is.
In reality, the roles that brands really play in our lives are multi-faceted, complex and individualistic. Where does the brand Audi stop and my car, Red Freddie, start?
Maybe we shouldn't try too hard to define a brand role, as long as we're clear what that brand stands for. In the end, it's the user who writes the film script of their life - and probably does the casting.