Not sure, rugged in context of describing someone means them having strong/sturdy features. Ruggedly in this case adds to the type of "handsome" and you can link that more to visual imagery and how it characterises "Big Brother" as an intimidating figure. You can also say its a historical allusion since "Ruggedly" connotes a sturdy figure which with "heavy black moustache" alludes to Stalin/Hitler. You can say Big Brother as a symbol is a culmination of those figures and is evident by that quote.