© 2019 IEEE. The IP Multimedia System (IMS) is an important reference service delivery platform for next generation networks and is considered as a de-facto standard for IP-based multimedia communication services. In its current design, the IMS faces important challenges in terms of scalability and elasticity, and lacks the ability to adaptively manage the network resources and dynamically dimension the network nodes based on load and demand. While Virtualized IMS deployments can partially address those limitations, IMS cloud providers still need to address challenges related to the high variability and uncertainty in their workloads, which could lead to poor QoS, high delays, and reputation and financial losses. The concept of cloud federation has been recently proposed to address such challenges. This concept enables a group of cloud providers to collaborate and form a cloud coalition that dynamically combines the participants' resources as needed, to meet variable users' demands. In this work, we propose a novel and customized IMS clouds' federation approach, that is inspired by the game theoretic roommate matching algorithm. The proposed algorithm aims at maximizing the coalition profit while minimizing the penalties incurred by violated SLAs. Our proposed solution was implemented and compared to the optimal and split-and-merge cloud federation formation approaches. The simulation results obtained show that our approach outperforms the optimal and the split-and-merge approaches in terms of execution time, while always yielding the same solution as the optimal approach in the cases tested, thus making it a strong contender for practical deployments.