Sessegnon in particular has come to life under Di Canio in recent weeks, helping the Italian secure back-to-back victories over Newcastle United and Everton.
The Benin international was on target in both wins, while Johnson scored from long range in a memorable 3-0 derby success at St James' Park.
Di Canio has declared that both players were sub-standard in the games prior to his arrival, but backed both men to flourish with his help.
He told The Guardian: "Stephane is a talent, a great player. If Stephane works as he's done in the last two games, he's a dangerous opponent but I can tell you, from the games I watched on television prior to signing my contract here, Stephane did not give his best.
"For me, your best is when you are playing with your brain and Stephane is now playing with his brain. But when I watched the Manchester United game on television Stephane only played when he had the ball or was in a position to ask for it.
"The players here are very good, Adam for example. If I say he can do even better, it's not a big criticism, it's just he has the qualities to play better but, game by game, we can improve."