Darkroaches are Category Unknown Undead spawned by the Stone of Sealing in the event the Joker Undead prevails in the Battle Fight and major antagonists in the final arc of Kamen Rider Blade.
Kamen Rider Blade
They are created in overwhelming numbers by the Stone of Sealing once the Giraffa Undead is sealed and Hajime Aikawa, the Undead known as Joker, is the victor of the Battle Fight. They serve Joker for purpose of destroying all life on the Earth prior to the Battle Fight resetting, targeting humans endlessly. When they die, they dissolve into green mist, only to be replaced with even more Darkroaches thanks to the Stone. Once Blade became the Navy Joker, the Darkroaches' existence was no longer needed.
Kamen Rider Decade
World of Diend
In the World of DiEnd, the Darkroaches are the minions of Fourteen, going after any one who breaks the law. Many of them are killed by the Riders and when their master is destroyed by Decade and Armed Hibiki, the remaining Darkroaches fade away into nothingness.
All Riders vs. Dai-Shocker
Other versions of the Darkroaches appear among the rankings of Dai-Shocker in the World of Decade.