"Roached out" is a term often applied to car bodies that have been sitting in fields and barns. The metal is corroded or rusted through in places, and overall it looks like something that roaches might be living in.
Mike Wolfe from American Pickers uses that phrase a lot. Anything that is corroded, rusted, flaking, splitting could be "roached".
This cent might be roached, but a 1946 Philly isn't anything special as far as I know. Was there some kind of key detail that isn't apparent?