Rosicky's previous contract had been due to expire at the end of the current season, while Mertesacker had 18 months to run on his deal.
"We are delighted that Mertesacker and Rosicky have committed their futures to the club," manager Arsene Wenger told Arsenal's official website.
"They are players of exceptional quality and experience, and have consistently proven themselves at the highest level.
"There is a great feeling of togetherness and belief in the group and this news will only help to strengthen this further."
Rosicky, who signed from Borussia Dortmund in 2006, is thrilled to be staying in north London and outlined his major ambition for the rest of his time there.
"One big factor is that I want to win the league with Arsenal," the Czech said.
"It's my big goal and I will do everything that I can to achieve it. Arsenal is a great club, we have a great spirit here and we are all working together to do the best we can.
"I'm very happy that I'm staying at the club. I'm proud that I'm still here after a long time and that it still continues. I'm glad I'm here at Arsenal and we’re all trying our best to win trophies for the club and our supporters."
German Mertesacker, who has developed a solid partnership with Laurent Koscielny at the heart of Arsenal’s defence, stated he was living out a boyhood dream by playing for the club.
"On my first visit to England as a boy I brought an Arsenal jersey as a souvenir and was so proud wearing it when playing football with my friends," he said.
"Many years later, I have become a real Gunner, being even more proud to wear the Arsenal jersey.
"I am truly thankful to the club and all the supporters for the time I have had here so far.
"And today I am deeply proud to have extended my contract with Arsenal. I’m proud to be a Gunner."
