Oritsé, who has enjoyed six years of success with JLS after the group appeared on X Factor in 2008, said 1D are a true X Factor success story.
"I'm so proud of them and they are an amazing boyband," he said. "It's another X Factor success story."
"Especially with Liam, when he was auditioning our year as a solo artist he didn't get through, and I said to him, 'you should be in a boyband'. And look at them now, I'm just so proud of them."
Oritsé, who wore a gold-studded leather jacket, walked down the red carpet at London's Leicester Square with band mates Marvin Humes and Aston Merrygold, although JB Gill wasn't present.
Taking to Twitter, Oritsé added: "Very proud of you boys!! Strength to strength!"
Aston also had words of congratulations, calling 1D "superstars". He tweeted: "Madness at the @onedirection premier MAD respect for these boys! True superstars well done boys!"
JLS will call it quits at the end of this year, following a farewell arena tour.
While Marvin will concentrate on his DJ-ing, JB with farming and Aston with songwriting, Oritsé will be putting his best dancing shoes on as he prepares to star in a new ITV reality show, Stepping Out, alongside his girlfriend A.J Azari.
Oritsé and A.J will will be joining five other celebrities and their real-life partners, including Brian McFadden and his wife Vogue Williams, and Denise Welch and her husband Lincoln Townley, to master a new dance genre each week.
After watching This Is Us with Aston, Marvin and his wife Rochelle Humes, Oritse continued his praise: "Great watching @Onedirection Premiere last night! Really enjoyed the movie! Very #Proud x."
Watch the trailer for This Is Us below: