Rorarii are often found in groups, and attacking one of them will cause any nearby Rorarii to become aggressive to the attacker. When an undamaged Rorarius is attacked, it will send off an "alert" in a 5x5 radius that will cause nearby Rorarii to attack the player. Sometimes, Rorarii may send out a second "alert", causing them to go into melee distance of the player and attack them from there.
For this reason, if you are being overwhelmed by multiple Rorarii, simply damage each one and kill them off normally. Corruption Shot is a good ability against Rorarii due to their low health and will prevent them from alerting nearby Rorarii to aid them.
As with all Ascension members, Rorarii have high melee and magic resistance, so it is recommended to kill them with ranged.
They also feature in Nomad's Elegy together with the other Ascension creatures. The Rorarii encountered in the quest do not require a Slayer level to harm, and are vulnerable to all forms of combat.