Ben's defeated an ancient Kel dor Battlemaster, outfought an amped Saber Gavar Khai, killed multiple amped Sith sabers while on Dromund Kaas, killed a nightsister in Backlash iirc, defeated Vestara Khai, etc.
In the force he's destroyed a TIE fighter while hindered by Ziost, by crushing it under tons of boulders, TKED a few Sabers, Tked a Rancor off a cliff, there might be some stuff I'm leaving out.
__________________ "Happiness is a lie. Life is horror. The light is always dying all across the universe. The last star will flicker out someday, when it does, all that remains is shadow. And I will be its king!"'-Amahl Farouk
Nah, they weren't really equals by any stretch of the imagination.
jaden was trusted, highly, by Kyle so much that he was given free reign on his missions, he advanced to Jedi Apprentice and obviously got better.
Where as Rosh stayed an Initiate, always had Kyle to help him out,had lots of help from the Kathos Twins when he fought Jaden, and, if you believe in it, was amped by Vjun's DS aura.
Not to mention the several reborn, cultist, stormtroopers, and Darth Vader level training droids that Jaden had to go through to get to Rosh.