Germany international Mertesacker, 29, has established himself as a key member of Arsene Wenger's first-choice back-four, playing alongside Laurent Koscielny for much of the campaign.
Rosicky also continues to form an integral part of Wenger's title-challenging squad despite being 33 and the Gunners' boss is pleased to have both players staying at Emirates Stadium.
"We are delighted that Mertesacker and Rosicky have committed their futures to the club," he 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."