Stuart Pearce's side were one of the pre-tournament favourites after arriving in Israel on the back of a nine-game winning run.
However, the Young Lions failed to deliver at this summer's finals, losing all three groups games, without scoring a goal from open play.
Jason, who started the first two fixtures against Italy and Norway, said: "Going into it we were full of confidence and rightly so given the form we were in.
"Obviously to put the performances in that we did was majorly disappointing. When you go to these tournaments, they're the times you're hoping it all comes together.
"It didn't on this occasion and that was very disappointing and frustrating.
"You have to just learn from it as best you can. Pick out what you could have done better, what you did well, learn from it and move on."
The Rovers midfielder admits he remains baffled as to why such a talented group of players didn't click when it mattered most and he was sad to see the curtain come down on his England Under-21 career in the way that it did.
"There's not one thing (I can put my finger on)," added Jason. "There's usually a catalogue of things when it doesn't go well.
"It's still difficult to say, because we had all the same players, the preparation in Turkey was fantastic, it just didn't happen for us on the nights.
"Personally, with it being my last tournament, it's very disappointing to end it the way we did.
"When you look back and realise that you've been involved pretty heavily with it and, first and foremost, it's great to get that experience of international football, of travelling away, playing against different styles and coming up against players from different cultures.
"It's all part of learning and helping in my development.
"I do look back and I'm proud, but obviously I want to win football matches and when it mattered we didn't quite do it.
"So it was disappointing to finish like that, but overall it was an experience I'll learn a lot from and take confidence from."
Having been away on international duty until mid-June, Jason was given some extra time off before being asked to return for pre-season training, but he admits it couldn't come round soon enough.
Speaking from Rovers' Portuguese training camp, he added: "You have a little break and after a couple of weeks you're ready to get back into it again, so I'm really excited for the new season and the challenges that will lie ahead.
"Everybody knows it's going to be difficult, you just have to get as much out of it as possible, run as hard as you can, because ultimately that's the base then for the rest of the season.
"Everybody knows it's going to be tough, it's just about getting through it, pushing yourself to the limit and making sure you're ready for the new season.
"From a team spirit aspect, getting away with just the lads is a good team bonding exercise. Coming away from the training ground, it's a change of scenery and it refreshes you a little bit, so that will stand us in good stead for when we go back."
After a turbulent campaign last term, Jason admits a feel-good factor has been reinstalled by new boss Gary Bowyer - a manager he knows well from his youth days at the club.
"I've been back a week now and the training sessions have been intense," added the versatile 21-year-old.
"The lads are buzzing, there's a good vibe and a good feel about the camp, so hopefully we can continue to work hard, continue to get better and then hopefully look forward and try to make a good start to the season.
"I've said it all along that Gary has seen what's worked and what hasn't. He's a very, very good coach, he studies the game and I definitely think he was the right man for the job.
"I'm just hoping now that we can all pull in the right direction and put the good times back in the club."