Career
Domestic Wallner began his career with hometown Sturm Graz in 1998. In the following year he moved to Rapid Wien, where he would have his most successful years, appearing in over 100 matches and scoring 42 goals over five seasons with the club He then spent one year spells at German club Hannover 96 and VfB Admira Wacker Mödling before signing with Austria Vienna in 2005.
He left the club in 2007.
At the beginning of the 2007–2008 season, Wallner signed a 1 year contract including the option of a 2nd year with Scottish Premier League outfit Falkirk F.C. In November 2007, Roman signed for Scottish First Division Hamilton Academical on loan from Falkirk, scoring once in four games against Stirling Albion.
He returned to Falkirk the following month. In January 2008, he travelled to Greece where he was on trial for the Greek Cup 2006-2007 winners Larissa F.C. In the same month Falkirk announced that Wallner had been released from his contract by mutual consent.
In late January, he signed with Apollon Kalamarias. On 3 February 2008, Apollon Kalamarias" player Barkoglou scored a last minute goal in a match against Olympiacos which ended 1–0 to Apollon.
Olympiakos appealed against Wallner"s appearance in the match, because according to Fédération internationale de football association rules a player could play for no more than two teams per season (having already played for Falkirk Football Club and Hamilton Academical), because of this Apollon lost the game in cards 0–3 and had 1 point deducted.
The case went to the jurisdiction of Chemical Abstracts Service. The appeal for provisional measures was declined. After the end of the Greek Superleague, Apollon Kalamarias was relegated and the deducted points would be inefficient to keep them clear of relegation. Therefore, the appeal against the first decision was withdrawn.
This fact, along with the claims by the AEK chairman Demis Nikolaidis and football players like Rivaldo, Traianos Dellas and Nikos Lyberopoulos that the Greek Football Association was responsible for this outcome, left the AEK fans with a taste of unjustice.
By then, Roman Wallner was one of the most identifiable and recnognisable football players in Greece and the controversy about his case will be remembered by all the Greek football fans in the years to come. International He made his debut for Austria in an April World Cup qualification match against Liechtenstein.