A huge goblin fan named Mad Goblin theorized that it's possible a parental figure of Roderick's was mentally insane hence why he keeps telling himself he isn't as such. The link to the MadGoblin stuff is in a ton of my Hobgoblin Roddy posts here. Just follow the Roddy/Hobgoblin tag and you'll find one of my Hobby posts that has the link.
I really wish Stern or somebody would get back to writing the Hobgoblin. He's such a great villain and I love to know more about Kingsley. But then again if he does return that sets him up for a fall. And honestly the fact that he's spent over a decade now in retirement with his criminal wealth is just such a perfect end for him.