Roger was first discovered under the ruins of castle in Romania by Liz Sherman, Bud Waller, and Sidney Leach. A homunculus is created from blood and herbs, stewed in a jar, and incubated in manure, and at first appeared lifeless to the B.P.R.D. investigators. He was activated when Liz touched the thing on his chest, and absorbed her pyrokinesis. Liz falls into a coma and is sent to the hospital. Roger is sent into a blind rage and eventually killed Bud Waller.
Hellboy and Kate Corrigan find Roger hopeing he can give Liz her pyrokinesis back, he's found praying to god to kill him and put him out of his misery. However he eventually runs into his brother who created a homunculus created from human fat in hopes of getting revenge on humanity. Hellboy tries to fight the homunculus but can't seem to slay it. Roger intervened asking his brother to "forgive him", his brother forgives him and he becomes part of the homunculus. Once Roger is part of the homunculus he uses Liz's pyrokinesis to melt the homunculus and his brother from the inside out. Roger eventually returned with Hellboy and Kate to restore Liz's powers to her.
Life at the B.P.R.D.
Years after the incident with his brother, Roger is saved by Abe Sapien from being dissected by the B.P.R.D. scientists just like Hellboy did the same for him. The B.P.R.D. gives Roger a mobile generator and makes him a field agent, but at the same time fitted a bomb on him to prevent anymore outburst of anger. Which was one of the factors that led to Hellboy eventually leaving the B.P.R.D.
Roger eventually proved himself as an agent after he managed to consume the Conqueror Worm, and kill Herman von Klempt. Although the Conqueror Worm almost destroyed Roger, he was saved by Lobster Johnson who used a lightning rod to shock the Worm out of Roger.
Roger was eventually promoted to a leadership role and controled an entire squadron of B.P.R.D. agents, but his cockiness proved to be his downfall when he was surprised by the Black Flame and was blown to pieces.
Johann Kraus communicated with Roger's spirit and asked him why he hasn't "moved on", Roger tells him it's because he's not human and his spirit has no place to go, but his spirit is in a peaceful dream world. Roger tells Johann that he's at peace and enjoys being dead, but wants his body to be buried like a man. Roger's body is buried under a false identity and his tombstone is engraved with the quotation "Great men are not always wise."