Rooney, 31, has scored in both Premier League games to begin his second stint at Everton, helping Ronald Koeman's men claim four points of a possible six.
The forward's goal against Manchester City on Monday was also his 200th in the Premier League – joining Alan Shearer as the only players to reach the milestone.
Jagielka lauded Rooney and said England's all-time leading goalscorer, who has not played for his country since November last year, “looks as good as ever” ahead of the Three Lions' upcoming World Cup qualifiers against Malta and Slovakia.
"With the season Wayne had last season – with him not being given the chance to play as much as he would have liked – he is concentrating on his football at Everton and if England comes knocking he has more goals to go for," the Everton captain said.
"He is England’s top goalscorer. I have been lucky enough to play with Wayne a number of times and he looks as good as ever now, as hungry as ever and hopefully that is a good sign for us.
"I am sure he will be happy. If not, we would be delighted he gets a rest and is ready to go for us."
Rooney made his return to Goodison Park after 13 trophy-laden seasons at Manchester United.
While the forward last scored at least 10 league goals in 2014-15, Jagielka said he never doubted Rooney would deliver for Everton.
"Wayne and his team-mates never doubted him – I am not sure why people would doubt him," he said. "He has proven, when he gets a chance to play a number of games, he normally scores a number of goals.
"His record for his country and for the teams he has played for has been second to none. So far, in pre-season and in Europe, he has been one of our best players. And hopefully that form will continue.
"He ran more than anybody else at Manchester City. He has been putting it in, he looks fit and sharp, and is scoring goals. There is not much more we will be looking for him to do."