RFID systems have been scrutinized nowadays as one of the emerging technologies in pervasive environment. And authentication becomes indispensible in applications where security and privacy are major concerns. Besides thwarting some major attacks, RFID systems need to be able to recover from unexpected conditions during operation. In this paper, we propose a Robust Authentication Protocol (RoAP) that supports not only security and privacy, but also recovery in RFID systems. The protocol can get back the desynchronized tags and readers to their normal state, and thus provides robustness. We also present a "safety ring" consisted of six major goals that have to ensure by each RFID system to be secured. This paper illustrates security and robustness analysis of the protocol. Finally, we present the implementation of our authentication protocol.