Cognitive radio users are allowed to utilize the unused portions of the licensed spectrum, which leads to performance enhancement. However, they need to carefully inspect the environment and make intelligent decisions. Secondary Users (SUs) are required to vacate the channel when a Primary User (PU) appears on the same licensed channel. This may cause interruptions in secondary network transmissions. In this paper we propose a distributed channel assignment scheme for cognitive radio networks. We consider a multi-radio node architecture in order to better utilize the multiple available channels. Our RIMCA (Robust Interference Minimizing Channel Assignment) scheme includes a collaborative sensing mechanism as well as channel assignment. We also consider channel reclaim by a primary user. When making decisions, secondary users consider the interference imposed on primary users as well as the total interference in the secondary network. Simulation results show that our RIMCA outperforms the most related channel assignment schemes. Moreover, our channel assignment scheme is robust to PU activities.