Kevin Fitpatrick's side were five point winners over Rosenallis.
Portlaoise recovered from an opening round defeat to book their place in the next round of the Laois Senior Football Championship.
Kevin Fitzpatrick's men came out on top against Rosenallis on a scoreline of 2-10 to 0-11, with goals coming each half from Chris Finn and Ricky Maher.
The 35-time winners have been drawn to face Arles-Killeen in round three after they lost to Killeshin by four points in the winners section.
Fitz' says they'll have to up their performance level the next day if they are to avoid the B championship:
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