An early strike from the Czech Republic international helped the Gunners to a 1-0 win over arch rivals Tottenham Hotspur on Sunday, their first away victory in the league since January.
The win sees Arsene Wenger's side climb into third place in the league, four points off leaders Chelsea with a game in hand, and Rosicky reckons there is no clear favourite for the trophy.
"I think it's a great race for the fans as well as the players," Rosicky told Sky Sports.
"I think it will be until the last game of the season.
"This is a very tough league, every game is very important and there are plenty of games still to go".
After exchanging passes with Alex Oxlade-Chamberlain, the 33-year-old fired in a superb 20-yard strike just 72 seconds into the game and he admitted that it was one to savour.
"It's one of the best, against Tottenham as well," he said.
"I'm delighted by a goal like that and most importantly we won the game.
"It's a great result for us. These derby games are always very tough. It means a lot for us, obviously for our fans as well. We are delighted."
Laurent Koscielny claimed the man-of-the-match award following a commanding performance at centre-back, and the Frenchman praised the work-rate of his team-mates during the win at White Hart Lane.
"All the players who were on the pitch tried to give themselves for the team and to win because it's a derby and it's for winning," he said.
"We communicate well on the pitch - it's very important for a centre-back.
"When we work very hard on the pitch we can win so we need to keep this for the end of the season."