The 20-year-old will link up with the League One club, where he enjoyed a successful loan spell last term, until January 3rd 2015.
A product of the Rovers Academy, O'Connell quickly progressed from the Under-18s to become a regular member of the Under-21 squad before earning league experience whilst on loan with both Rotherham United and York City in 2012-13.
But it was last season whilst with Rochdale that he really caught the eye, making 45 appearances at the heart of their defence, as Keith Hill's side clinched promotion to League One.
Capped for England at Under-19 level, the central defender signed a new two-year deal with Rovers in the summer, before making his first-team debut in the Capital One Cup against Scunthorpe United last month.
O'Connell is expected to go straight into the Rochdale squad for their Johnstone's Paint Trophy match against Crewe Alexandra on Tuesday evening.