From The Heretic Knowledge Vault
Little is known about Rokku, since he's not appeared in the actual comic and possibly only exists in the Fun with Familiars continuity/omake. He first appears in this comic. Before his first appearance within FwF, a pencil sketch of him (wearing an Exploitation Now shirt no less) was posted on the forums here.
At this point, Rokku is most notable for being Locke's owner.
According to FwF author Jim Hanson, Rokku attended the Sashi Mu Academy of Thaumaturgy and Conjuration where he was an honor student until his final year, at which time he was expelled under "complicated" circuimstances. The full details leading up to his expulsion have not been revealed yet, however it was revealed in his debut strip that whatever the reason, it's his classmate Kureji's fault.
Rokku has had a brief cameo in the Errant Road free-form role-playing game. He and Kureji (and Locke) appeared briefly in an encounter with Layla at the Gewehr hideout south of Kiyoka, in a case of mistaken identity. Rokku himself hasn't been seen in Errant Road for some time, but Locke is still there and would like to get back to his owner, sooner or later.