Rorarii were soldiers who formed the final lines, or else provided a reserve thereby, in the ancient pre-Marian Roman army.
[1] They may have been similar in role to the accensi, acting as supernumeraries and filling the places of fallen soldiers as a battle or campaign wore on.
Alternatively, they may have been skirmishers akin to velites as stated by Livy in Book VIII.8.
Unfortunately, the evidence is so limited that it is difficult to understand what direct role the rorarii may have had, if any, in fighting.
This article about the military history of ancient Rome is a stub.