idunn ends up being the leader of the warden gang simply due to having had experience in the carta- she knows how to be a leader out of all of them, and is the one who takes initiative to make decisions. she's the one willing to shoulder the consequences of tough choices. she effectively becomes the big sister of them all as well.
the party face however is cousland, she's very charismatic and likeable and has an in depth knowledge of ferelden politics, so she does the majority of the talking to people. she's also the one who handles most of the landsmeet and obtaining allies and negotiating treaties, and also anything that involves the group finances.
their main tactician and navigator, and also the guy who suggests where they should go next and does all of the travel and camping planning is felraaven. given his experience among the dalish, he's the best candidat. he was also the second to the keeper, so he has extensive knowledge of various things, including, intersetingly, battle tactics.
cinna is the one making sure everyone doesn't starve, or get poisoned, or sick, or just in general get stabbed and die. he's also the one studying the treaties and the places that they're headed to, so that he can collaborate with idunn and cousland on how best to approach the people they're going to be trying to win over. he fills a sort of advisor role and reasearcher, as well as 'the only person here who can cook'.
finally, embrium is mainly a scout and infiltrator, being sent ahead of the group when traveling or planning to go into a new place to check it out. aside from that, they take a less active role in the warden group's planning and stuff, mostly because they have 0 social skills and jump to trying to stab people WAY too fast in basically any situation. theyre good with explosives and poisons too, which is. alarming. but useful when planning defenses of places like redcliffe and denerim.