Most but not all of his roles are minions or ruffians. If he plays a good guy, he's likely to be a male Tsundere. He also boasts a notably wide vocal range, capable of producing both a Creepy High-Pitched Voice and a Baritone of Strength.
Some of Masami Iwasaki's roles are:
- Alfonso in Gunslinger Girl
- Bighorn in Beast Wars II
- Hardhead in Beast Wars Neo
- Build Cyclone and Wrecker Hook in Transformers: Car Robots
- Dr. Emmanuel Klipse in the Japanese dub of Monsuno
- Fyodor Patrichev in Legend of the Galactic Heroes: Die Neue These
- Hanayaider in Doubutsu Sentai Zyuohger
- Iemitsu Sawada in Reborn! (2004)
- Iruka in Jewelpet Sunshine
- Isono (Roland) in Yu-Gi-Oh!
- The Jikochuu in Doki Doki Pretty Cure
- Karasu Yumeshima in My Mental Choices Are Completely Interfering with My School Romantic Comedy
- Keisuke Itonokogiri (Dick Gumshoe) in the anime adaptation of Ace Attorney
- Koji Kuroki in Eyeshield 21
- Lotten (Lawton) in Yu-Gi-Oh! 5Ds
- Norway in Hetalia: Axis Powers
- Power Shark in Beast Saga
- Raoh in Fist of the North Star: Lost Paradise
- Ryuji Goda in the Like a Dragon series since Yakuza 2
- Headmaster Samejima (Chancellor Sheppard) in Yu-Gi-Oh! GX
- Sakekaasu (Seaslug) and Prof. Otokoyama (Coach Mountain) in Medabots
- Skyquake and Dreadwing in the Japanese dub of Transformers: Prime
- Yoshiro Akazawa and Hiyoshi Wakashi in The Prince of Tennis
- Yokumiru Mera in My Hero Academia.
- ZZ in JoJo's Bizarre Adventure: Stardust Crusaders
