As well as raising a personal grievance, Ms Roskam laid a formal complaint with the police, but an investigation concluded the allegations lacked substance.
Instead, police charged Ms Roskam with making a false complaint, but the charge was withdrawn at a formal hearing.
The ERA heard the Christmas party incident took place after Mr Fallows attached a bottle opener to his Santa costume at the urging of a group of female staff members.
He tried to resist but buckled after the fifth or sixth approach.
Ms Roskam said she found it humorous at the time, as did most of those around her. It was only later that she complained.
She also alleged Mr Fallows made improper comments and physically assaulted her.
On one occasion, she claimed, Mr Fallows came up behind her while she was loading sheets on to a conveyer. She said he grabbed her and began thrusting his pelvis repeatedly into her bottom, which made her feel "absolutely sick and violated".
She said he only stopped when a co-worker saw what was happening - a claim the co-worker rejected.
Mr Fallows said outside the hearing he was gutted when the allegations were levelled against him: "I was in shock."
The allegations were not true, he said. Mr Fallows had "no idea" why Ms Roskam had complained about his behaviour. APNZ