Rogic set to get Celtic opportunities
Rogic, 22, endured a difficult 2014-15 campaign with injuries – failing to make a senior appearance for the Scottish league champions.
But the nine-time Australia international trained with the first team on Wednesday as he aims to break in at Celtic.
In a media conference, Deila was asked if players like Rogic had a clean slate ahead of the new season.
"Of course," he said.
"Everybody starts now to try to show themselves.
"They will get opportunities in the games now in pre-season and if you do good performances, everything is possible."
That comes as good news for Rogic, who has made just 15 appearances in all competitions in two-and-a-half seasons at Celtic.
Deila is seemingly keen to see players like Rogic get their chance to train with the first team.
"I'm very happy with the squad I have. We have many players. I think we need to get a smaller squad as well," the Norwegian said.
"It's not only to get players in, it's also to get the right team, the right squad together into the season.
"As you see today, there was a lot of youngsters at training with the first team and that's also because we have room for them and that's important in the future as well to get the youngsters from Celtic to get an opportunity to train with the first team."
Celtic's pre-season friendlies include games against Den Bosch, Dukla Prague, Real Sociedad, Eibar and Rennes.
Deila's side also face Stjarnan in the UEFA Champions League second qualifying round.