Roach was killing the weird before Deterrence got their hands on him. Putting himself in the classifieds as a solver of meta problems, he was contracted solo to deal with superhumans on the Australian subcontinent when the authorities either weren't enough, or weren't wanted to be involved. Roach's unnatural aptitude along with his ruthlessness made him a competent eliminator of threats he should by all means stood no chance against. Why Roach is so obsessed with killing metas has never been revealed - nor does anyone know anything about his background, which appears to have been scrubbed from all official records. People just know him as "Roach, that guy who'll kill your supervillain if y'e've got one."
Though all analysis confirms that he is a normal baseline human, his incredible resistance along with uncanny pain tolerance has led some to suspect he harbors some form of superhuman durability. In reality, he might just be some combination of lucky, determined, and insane. Roach's first big break was in disposing of a pyrokinetic with extreme ballistic resilience. Strangling the foe, he sustained radical burns on his forearms, but not before collapsing the attacker's windpipe and incapacitating them for good. From there on out, he was the top meta hunter in the Southern Hemisphere, sustaining an entire business operation completely on his own as a bounty hunter with a specialty in bringing in superhumans. Deterrence recruited him before any competition could, banking on his independent nature and low-key profile.
Roach had his nickname long before it became his official callsign with Deterrence. In fact, it's the only name they have on record. An absolute loner, he refuses to work with any backup, and doesn't even generally identify as a member of the Hypercorp. They're a source of pay, gear, and orders - nothing more. The Security Nation is fine with this distant relationship, letting Roach do as he pleases so long as he's loyal at the end of the day. He takes side jobs continuously, and works best as a covert agent - someone without ties to the corporation who can handle more clandestine problems.
Roach is mean, bitter, greedy, violent, deceptive, vengeful, ugly, and he stinks. But, atop all of these, he's creative, practically ingenious when it comes to handling exohumans, and resilient enough to tank hits from them and keep on fighting. He has no ID, living totally off the grid. Nobody knows he exists outside of his old business. Ruthless and experienced, his complete independence makes him a valued asset to the Security Nation...
...even if they prefer to keep him a secret.