Well, like I said, I don't want to make to much of their culture up since that might restrict the creativity of the adopters forms. But, well... This is how I see it.
Atwood is closest by far. Most roles that don't need a hightly special competence (being elder for example, demands that you are old) will be shifted around and done by whoever is able. Since the elders does most of the hard desitions, they are also the groups leaders. Of sorts. They don't go fighting about the leader position, no one would try to kill the current leaders (elders) to sieze power for itself. It wouldn't happen. If it would, that smili would never be accepted as a leader but most likely killed by the rest of the group. The oldest and wisest should lead, the strongest should hunt, reproduce and do whatever a young adult smili is good at. It's simple logic for a smili. And if the young one gets the honour of living a full life it would get a chance to become a elder then, when the place is rightfully earned by experiance.
I never thought smili to be a religious sort, so if they do have some sort of belif it's based on a desire to understand the world around them rather than an acctual worship. It could be in the shape of the tales the elder tell about the world when they were young, and from their parents and grandparents. Keeping history alive from one generation to the next. Trying to form a story about the beginning of the world. I don't think a special role is needed for this, but it would be cute if it was. A elderly smili who might als know a bit of herbs and can tell all the tales. A shaman role of sorts. I don't know their thoughts about "after life" but I doubth they spend their time debating on the existance of a soul. They are practical beings and I don't think such thoughts cross their mind much.
No healers, it sounds like it's straight out of a Warriors book. Mostly injuries are fatal, broken bones and simple infections is deadly for the smili. If they survive they still might be crippled for life, if for example, the bones heal in a strange angle. They lack proper care ang hygene of modern society. A wonded smili would be taken care of by it's family or elders, possibly the "shaman" if the particular group happened to have one. I don't think their heling skills goes any further than licking on wounds, possible chew on this stick-that-makes-you-ever-so-slightly-drowsy. No miracle herbs. Nothing more fancy than salix tree, sure, salix works and it grows like weed practically everywhere, but it's not very effective.
I like the idea of caretaking, seen among for example lions and meercats, but that could be done by any older sibling who is to young to hunt, or any elder who is to old. There would mostly always be smili left behind in "camp", so there wouldn't need anyone in particular to care for the cubs.
All artistic expression is done on spare time since hunting for food is rather more important. It's possible that other smili would spot the best artisan to ask for jewelery or a body painting. Then it's sort of a role, I agree on that.