The Lions have three days to respond, but are expected to pass up this option to claim the compensation draft pick for their former captain.
Rockliff, 27, will join the Power to enhance Ken Hinkley’s midfield rotations.
He will leave the Lions after 154 games since 2009 and with his honours as a Brisbane player including two club champion titles (2011 and 2014) and All-Australian selection in 2014.
The Power is now waiting on Geelong free-agent midfielder-forward Steven Motlop to settle on his next contract with either the Cats, Gold Coast, Adelaide or Port Adelaide.
The Power also is seen as the frontrunner for contract Melbourne key position player Jack Watts who has Geelong and Sydney also seeking his signature.
Hinkley has noted all three prospective recruits address Port Adelaide’s need to find more power to hit the scoreboard next season.
Port Adelaide will now lose its compensation draft pick (currently No 30) that was assigned by the AFL last week when Jackson Trengove took up free agency with the Western Bulldogs.
Brisbane is expected to be handed draft pick No. 2 as compensation for releasing Rockliff to a free-agency move.