Joao scored both of Wednesday's goals at Hillsborough - the second and third in his last three outings, a run in which he also won a penalty for his side at Barnsley on Saturday.
The twice-capped Portugal international confidently dispatched a Jack Hunt cut back to put the hosts in front early in the first half, before firing in from range to double the advantage soon after half-time.
However, it wasn't just Joao's goals that stood out, with his work rate and hold-up play also impressive.
And speaking to the Sheffield Star afterwards, Rowett admitted: "I thought Joao was excellent. At times he was unplayable. He shows he's very unpredictable and difficult to get the ball off.
"But to allow him to turn and to allow him to have that much space is very unlike us, and then it's a fantastic finish from him that Scott Carson couldn't do much about."
He added: "I don't think Scott's had a save to make the whole game, and if you look at their goalkeeper and defenders they have had to work incredibly hard to keep the ball out."
Joao has started five of Jos Luhukay's six league games as Sheffield Wednesday manager, having begun just three of a possible 26 under the Dutchman's predecessors Carlos Carvalhal and Lee Bullen.
Speaking to the Sheffield Star afterwards, however, Luhukay was keen to see the credit shared after securing his first non-cup win since taking the reins at Hillsborough.
"Lucas was very strong and played well with his colleagues," he said. "I’m very happy with him. He is a very important player for us. But Jordan [Rhodes] also worked hard."