Super OP person (Monika?) looks like a woman mage knight (page 7). I think given what we can infer from the harem tag, she will be joining the harem eventually after a fight or "misunderstanding". Also, isn't our MC a paladin/mage knight too? Monika probably has the same class or is a secret admirer (if the cliche holds).
But really the entire problem/issue can be traced back to Tabatha the guild girl failing her job. She seems to be an epic fail of a guild receptionist thus far. Like how bad does one have to be at their job by failing to communicate basic job description and advising/disclosing the job hazards?

For a "hero's party", Tabatha sure didn't give much of an effort to investigate or mediation to manage the party's grievance. One would think the guild would at least put an effort to keep the hotshot party together lest they end up harming the guild's reputation and/or revenue if they split.
In a competent organization built on trust, if Ellie bothered reporting Roland to the guild for his rpe attempt, he would be blacklisted or at the very least suspended pending an investigation. Of course, again - this is all depending on Tabatha doing her job.