No matter how they portrayed Roxie. It doesn't change that Ash couldn't have beaten her 3 on 3.
That's not a show of how strong Roxie. It's a show of how weak Ash is.
His Pokemon all took out powerful Pokemon at some point in the Best Wishes saga, and yet only Leavanny, Pignite, and Pikachu managed to do anything of importance.
Seriously how weak are they? They must be pretty damn weak. If Ash can't handle a gym leader without using a full team against half of a full team, then he's NO WHERE near the level of being able to compete in the league.
There are trainers who are likely supposed to be a lot stronger than Roxie. Of course the writers don't give a crap about that, since they're known to make things look as unbelievable as possible.