
Quick answer — Naoya Nosaka voices Oliver in Violet Evergarden, Servant in Thus Spoke Rohan Kishibe, Tadanao Shiraki in Tamako Market and 2 more characters.
Naoya Nosaka voices Oliver (Violet Evergarden), Servant (Thus Spoke Rohan Kishibe), Tadanao Shiraki (Tamako Market), Rowan (Guilty Crown), Taishou (Headhunted to Another World: From Salaryman to Big Four!).
Oliver is voiced in Japanese by Naoya Nosaka.