
Quick answer — Ryouichi Tanaka voices Devilman in Devilman: The Birth, Keimusho Shochou in Baki Hanma, Death Mask in Saint Seiya: Knights of the Zodiac and 4 more characters.
Ryouichi Tanaka voices Devilman (Devilman: The Birth), Keimusho Shochou (Baki Hanma), Death Mask (Saint Seiya: Knights of the Zodiac), Kozo Saito (Akuma Kun), Zenzo Saeki (Koi Kaze), Takeshi Maki (The Devil Lady), Rou Dai Kaioshin (Dragon Ball Super: Beerus).
Devilman is voiced in Japanese by Ryouichi Tanaka.