Blitz Rods are mob drops added by Thermal Foundation. They are sometimes dropped when a Blitz is killed. Essentially, they are the Blitz equivalent of Blaze Rods.
Blitz Rods only have a single use: they can be crafted or pulverized into Blitz Powder. This material is a critical ingredient for creating Aerotheum Dust and, ultimately, Zephyrean Aerotheum.