@Burthstone Rosalina's team mostly functions as any Rune Knight would. They patrol, guard and enforce the law. However rather than be stationed in one spot, they are almost always within a couple hours to a day of Rosalina's position unless instructed otherwise by her. Rosalina as the leader of the Knights and a Council Member trusts them to be an extension of herself when required.
This essentially means that any delicate tasks that would not normally be required of a Knight are undertaken by her specialised unit who are granted her high ranking clearance and authority for the duration of said task. Though this responsibility usually falls on Constantine, as she is the most trusted to use Rosalina's power appropriately. Bayard is too emotional and righteous whilst Zen is too young and inexperienced (Which will most likely be the same justification used for why Luna cannot hold that power even though she outclasses all of them in terms of Magic Ability).
Basically, Rosalina's team is capable of acting in place of her as a Council Member when on certain tasks that she herself cannot attend for whatever reason. That is of course if the GM's of the RP are okay with that (
@Caits,
@Zarkun,
@Expolar).
The tasks they undertake can range from anything from a simple diplomatic meeting or investigating a Dark Guild. Sometimes they may even be put into a position where they as Rosalina's acting voice need to make a judgement on an individual or group for alleged crimes. Any action they decide to take can be overruled by any existing Council Member at any notice. Where applicable they are advised to use communication Lacrima to gain clearance on any decision from Rosalina or another Council Member but this isn't always convenient.
Other than that, they also train together as any team would. Their strategy is synergy and they have a very firm belief in the whole being greater than the sum of it's parts. Rosalina doesn't usually have any part in training them, though she does make time for Zen wherever possible. In fact it's very likely to assume that once joined, Luna's contact with Rosalina will be minimal compared to the time she'll spend with Zen, Constantine and Bayard.