The 27-year-old has been without a club following his release by Brighton at the end the 2012/13 campaign.
The Irishman says he is looking forward to playing under Dale boss Keith Hill.
He told the club's official website: "The move came about pretty quickly and I'm looking forward to getting back out on the pitch.
"Because you haven't signed for a club straight away people think you are holding out for this or that but it wasn't the case. I spoke to a few clubs but for whatever reason things didn't work out.
"I spoke to Keith Hill and thought about the move for a bit. I spoke to a few players who have played under him and they all think highly of him so I think it'll be a good move for both of us.
"I have good memories playing against Rochdale and they have always put up a good show against the teams I have played in. There was Wembley and two great games when I played for Brighton, we drew two apiece so I know what Rochdale is all about.
"I'm looking forward to working with the gaffer too, I know him from his time at Rochdale and at Barnsley and you pick it up as a player how certain teams play. Keith Hill's sides play good attractive football and that will suit me."