Incidents caused by fire and combat operations can heat energetic materials that may lead to thermal explosion and result in structural damage and casualty, thus understanding the response of energetic materials to thermal insults is crucial for the safety design and assessment of insensitive munitions. In the present work, cookoff characteristics of a new DNAN-based cast explosive ROL-1 are systematically analyzed. Small-scale slow cookoff experiments were performed and an overall reaction kinetic model including the melt-ignition model for DNAN was developed and implemented in FLUENT. The simulated results agree well with the experimental data, which verifies the validity of the model. The large-scale fast cookoff experiment and simulation were then performed. Ignition behaviors as well as the reaction mechanism of ROL-1 under slow and fast cookoffs are investigated. The heat generation rates are highly correlated to the temperature gradient, liquid phase fraction, and ignition behaviors in ROL-1. The ignition of ROL-1 happens at around 550 K, delaying the ignition temperature of the HMX (493 K) by nearly 60 K, indicating the potential substitution of NTO for HMX. The safety of ROL-1 has proven to stand out in comparison to a range of mixed explosives.