Keep the goal in mind:
Experiences in residence life, even roommate conflict, are an opportunity for learning how to do relationships well. Our goal isn't to simply solve the problem for them, but to help them engage in healthy conflict and grow through the process.
First Step: Encourage Them to Talk to Each Other
When a resident comes to you with a concern, you're first priority is to simply listen well.
If they haven't spoken to each other about the issue, encourage them to have a good conversation about it and coach them through some principles on assertiveness.
Second Step: Help Them Talk to Each Other
Once you feel they've spoken with each other about the issues and the issues are ongoing, then it might be time for you to step in and help facilitate a conversation.
Speak with each individual separately before meeting all together to balance your role in the mediation.
Schedule a 1 hour meeting time. Use a neutral location such as your room or the AC/GA Office (ask your AC/GA first).
Start by articulating the goal (mutual understanding and finding a way forward), discussing your role as a facilitator, and laying out your expectations for them.
Ground rules: 1) Speak for yourself by using "I" statements. 2) Don't interrupt. 3) Avoid blaming. 4) Talk to each other, not to the facilitator. 5) If it's not going well, you'll end the meeting and reschedule.
Invite one person to share un-interrupted about their experience of the relationship. When they're done, have the other person summarize what they heard and work towards mutual understanding. Then switch. Then allow them to offer responses. Then transition focus to finding a way forward.
Set an alarm for 50 min, and when that goes off, let everyone know you have 10 more minutes.
Often, roommates will be able to find a tentative solution. Encourage them to give it a week or two. Check in with them to see how it's going.
Third Step: Seek RD Facilitation and a Potential Room Change
If things still aren't going well, then I will step in and offer another mediation and consider whether a room change is appropriate.