Oldham pushed for an opener early on and they nearly found it through Rooney, whose long-range effort flew just wide of the post in the third minute.
The home side had a good chance minutes later as Danny Haynes got on the end of a cross, but the striker's header flew just wide.
Notts County took the lead in the 20th minute, however, as Haynes converted Greg Tempest's cross with a neat header from the centre of the box.
County pushed to take their lead further as Jack Grealish saw his headed effort creep wide. However, Oldham grabbed an equaliser through Rooney right on the stroke of half time as the sides went into the break at 1-1.