Throughout the series Kenshin has added 'oro' somewhat comedically to his sentences. Is there any actual meaning to this or is this just a speech style/pattern that he has?
From Urban Dictionary:
A Japanese expression of confusion. Often used by otaku to indicate confusion/disorientation. People who read/watch "Rurouni Kenshin" may pick up the habit of saying "Oro!" because Himura Kenshin says it often in the manga/anime.
From Wikipedia page on Himura Kenshin:
Nobuhiro Watsuki added Kenshin's trademark "oro" as a placeholder to be an expression of the English speech disfluency "huh". Watsuki notes that he was surprised at how much it caught on, and how much he ended up having Kenshin use the sound during the series
You can watch a few of his Oro moments here (and see that he usually uses it when he's confused/disoriented).