"Nothing is impossible," states the body art in Irish Gaelic. It is a mantra which the 25-year-old striker - who has signed a two-and-a-half-year contract at Pittodrie - is likely to be asked to underline after his return to Scotland, with Rooney expected to make his debut tomorrow in an SPFL Premiership's against Motherwell. The Irishman's arrival was confirmed yesterday after he had earlier been released by Oldham Athletic just six months into a two-year contract.
It is up front that Aberdeen have been found wanting this term. Scott Vernon, who has been re-established as first-choice striker, has proved impotent with a measly three goals in 12 league appearances, while summer signing Calvin Zola has all but drifted off the radar and Josh Magennis has been introduced fleetingly in games when his side are in need of an energy boost.
McInnes have not have struck gold with Zola - Vernon and Magennis were already at the club when the manager took over from Craig Brown - but Rooney has the potential to be a different and better proposition for a club which is second in the league table. McInnes was acquainted with Rooney's talents already, since he had tried to sign the Irishman while in charge of St Johnstone.
"Way back when he was at Stoke, we tried to take him," said McInnes. "Tony Docherty [his assistant] and I went down to see him a few times when he was scoring in the reserves at the Britannia Stadium when he was 18. However, he chose Inverness Caledonian Thistle, who were able to come up with the figures required.
"When he left Inverness and joined Birmingham City he had earned his move to the Championship. He went to a couple of clubs - Birmingham and Swindon - that weren't the most stable in terms of their ownership. He will help us in the challenges that we face in the short term but the fact we have secured him for a further two years is important as well."
Rooney blossomed under Terry Butcher during two years at Inverness, scoring 44 goals in 103 matches. That ratio caught the eye of Birmingham and the striker was taken to St Andrew's by Chris Hughton when his contract in the Highlands expired in the summer of 2011.
"I have heard a lot of good things about Derek and Tony Docherty," said Rooney. "They have built up Aberdeen, told me how big a club it is and where they want to get to. It was something that really excited me."
Butcher had tried to persuade the Dubliner to join his revolution at Hibernian, though the player declined to be drawn on that issue. His focus is already settled on Aberdeen and a trip to Fir Park. "This move interested me most," he said.
"The cup games [the League Cup semi-final against St Johnstone next weekend and then a Scottish Cup tie against Celtic] will be great for the fans but the main focus has to be Motherwell."