Randle, who was arrested in an unrelated incident Monday for the fourth time in the past year and a half, was released on Nov. 3 because the Cowboys wanted him to get counseling to help him deal with his off-the-field issues and he refused, two sources told ESPN's Jean-Jacques Taylor.
The Cowboys believed they had no choice but to release Randle because they couldn't trust his behavior, the sources said.
In a text to the Fort Worth Star-Telegram, Randle, 24, said there is "no truth at all" to reports of his sports gambling.
At last week's Senior Bowl, Cowboys owner Jerry Jones said there was no evidence that Randle ever bet on the NFL or attempted to influence the outcome of Dallas' games.
"Not to my knowledge, not in any way," Jones said.
"There are certain types of gambling that you can't do as a player," he said. "Obviously you can't be involved in ... anything that we're competing in, and I've never heard of anything like that."
NFL spokesman Greg Aiello said he was unaware of any league investigation into Randle.
"We have never had any information relayed to us alleging that Joseph Randle bet on sports," Aiello said.
While the team did not previously mention gambling as part of the reason for Randle's dismissal, Jones acknowledged as much last week, adding that Randle's mental health was another issue that led to the team parting ways with him.
"All of that became apparent to us right during the season," Jones said. "Not before the season. It became real acute, a combination of things. Some issues ... became more apparent."