The breach did not involving leaving the national team's Covid-19 bubble and is thought to be more about not respecting curfews within the team hotel, but was considered serious enough for Roberts to be sent home ahead of Tuesday's World Cup qualifier at home to the Czech Republic, along with Hal Robson-Kanu and Rabbi Matondo.
It must now cast doubt over the 22-year-old's participation in this summer's European Championships, despite him having started this month's friendly win over Mexico, and come off the bench in the World Cup qualifier defeat in Belgium. The Mexico game earned him his 13th international cap.
“Gutted to be leaving the camp early but rules are rules and I shouldn't have been up in the hotel later than the set time,” Roberts wrote on his Instagram account.
“Sorry to the team, staff and Wales fans.
“I will continue to work as hard as I can to earn my place in the squad for the Euros.”
Wales are in a European Championships group with Turkey, Switzerland and Italy having qualified through the play-offs.
In announcing the news, the FA Wales said it would not comment further.
Leeds's next Premier League game is at home to Sheffield United on Saturday.
Support The Yorkshire Post and become a subscriber today. Your subscription will help us to continue to bring quality news to the people of Yorkshire. In return, you'll see fewer ads on site, get free access to our app and receive exclusive members-only offers. Click HERE to subscribe.