Oddly, this monster appears heroic in design as opposed to its comrades, and uses much more light coloring. In "Advance Zone", Steelswarm Sentinel is being surrounded by what appears to be a "Vylon" artifact, suggesting that the "Vylons" tried to purify "Sentinel" and created "Roach". This means that it can either be barely infected by the "Evilswarm" virus, or else is completely immune, making it the only "Steelswarm" to retain its true form.
Due to the absence of the "Steelswarm" archetype in Duel Terminal - Xyz Startup!!, it may be that they were defeated by the combined forces of their enemy archetypes, or possibly destroyed themselves by accident in the plague that created the "lswarm"; either way, "Roach" is the only prevalent member left, which references it being named after an insect that is known for its survivability.
In the OCG, the name of "Steelswarm" monsters that are Level 5 or 6 starts with "M" (probably for "Medium" or "Mega"), while those who are Level 7 or 8 starts with "G" (probably for "Great" or "Giga"). This card does not have a Level, but instead a Rank, likely the reason why "Roach" begins with "R".