This document proposes and evaluates a random access cooperative spectrum sensing method for cognitive radio networks. It describes using a Reservation ALOHA (R-ALOHA) protocol to design the reporting channels between sensing nodes and the fusion center. The key advantages of this approach are that it reduces complexity compared to fixed channel assignment and allows good sensing performance with a limited number of reporting slots. Analysis and simulations show the R-ALOHA approach performs better than previous methods and can achieve low false alarm probabilities even with 10 reporting slots. The maximum throughput of the R-ALOHA system occurs when the load factor is equal to 1.