Droid grenadiers functioned as a variety of B1-series battle droid inside the Separatist Droid Army. Several grenadier units were part of the droid force tasked with protecting the Separatist droid factory located on Thule during the events of 22 BBY.
The first canon appearance of grenade droids was in Inquisitor: Rise of the Red Blade, a novel written by Delilah S. Dawson; however, they had previously appeared in Star Wars Legends material. Dawson found the Legends version of the grenadiers on Wookieepedia while she was researching whether a droid unit of this type existed, and she chose to include them in her novel. In response to a fan's question about whether the grenade droids in her novel were a B1-series variant, she verified that they were indeed a canonized version of the Legends B1 grenadier class.