Rodio said the casino was trying to determine whether the workers should be fired.
"The employees that blocked the entrance and engaged in illegal activity have been suspended indefinitely," Rodio said.
"This is conduct that got them arrested by the police," he said. "This isn't a free-speech issue; they broke the law and interfered with our business and our customers. Frankly, I can't see how they didn't think there would be repercussions from that."
The 21 employees represented all the Tropicana workers who were arrested at the protest. The workers were charged with refusing to obey a police order and blocking a roadway and were released on summonses to appear in Municipal Court.
The casino was evaluating internal disciplinary cases Tuesday, and Rodio said it was possible the workers could be fired.
"Consider any other business," he said. "If you had a disgruntled employee who laid down and blocked the front entrance of your business and wouldn't get up for an hour until he was arrested, how eager would you be to have that employee come back to work for you?"
The union said its members were exercising their free-speech rights on their off hours and should not have been suspended.
Francine Stevenson marked her 17th anniversary with the Tropicana on Tuesday by getting a suspension notice. She is the grandmother of two girls, including one who just graduated from high school and is off to college.
"I feel very angry and upset about what has happened," she said. "We finished our shifts, clocked out, walked outside, and did our union activity. We didn't destroy anything; we were totally peaceful. We weren't even on their property."
She vowed to continue to fight the casino's termination of its employee pension plan.
"My father is 81 years old, and he had to go back to work driving a truck because he has no pension," she said. "It is just not right what companies are doing to their workers. That's why I feel so strongly about this."
The dispute centers on a protracted contract stalemate between the union and the Tropicana, which is one of the three of Atlantic City's 12 casinos without a current contract with Local 54.
Bob McDevitt, president of Local 54, said the Tropicana broke the law first by refusing to bargain in good faith and by unilaterally declaring an impasse in contract talks and terminating its pension plan.
"Tony Rodio is behaving like a bully, trying to intimidate the workers," McDevitt said. "Tropicana has suspended 21 people who exercised their First Amendment right to protest Tropicana's illegal refusal to bargain and to try to make life better for themselves, their families, and their communities.
"Tony Rodio is a local who has turned his back on his workers and his neighbors, and we hold him fully responsible for Tropicana's shameful behavior," he added.
Rodio said that unless the union ended its campaign against the Tropicana, the casino would scrap its planned $100 million worth of capital investments in the property, $25 million of which is due to begin in September with room renovations and other work.