If Facebook introduced the rooms feature to encourage meaningful interactions among users, the success metrics would primarily focus on engagement and retention. I would monitor the daily, weekly, or monthly creation of rooms, along with the average number of participants in these sessions. Another important metric would be the length of time users spend in rooms and the frequency with which the same users return. Additionally, I would suggest tracking the percentage of users who go on to create their own rooms after participating in one. Gathering both qualitative and quantitative feedback is crucial for assessing user satisfaction and pinpointing areas for improvement. Finally, potential monetization avenues, such as collaborations with brands or advertising, could also serve as valuable indicators.