The red field around Rollo seemed to indicate his Geass has an affect area around him. Geass obviously affects how the brain works, but so far we've seen eye contact and the one the psychic had which didn't (iirc) need eye contact at all. So naturally you can assume there are different methods to affecting the brain that don't have to be based around close/eye contact.
as for the episode one thing, I'm not sure. maybe he had already used his geass before the explosion and wasn't anywhere near it.
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