The Czech international starts his first game of the season while the youngster is handed his full debut at left-back after appearing in Capital One Cup win over Reading
Arsene Wenger has made seven changes from his team that lost to Swansea City in the Premier League on Saturday, with top spot in Group B already assured.
Only Wojciech Szczesny, Carl Jenkinson, Thomas Vermaelen and Gervinho have kept their place from the defeat to the Swans at the Emirates as Jernade Meade makes his full debut at left-back, while Sebastien Squallaci makes his first appearance of the season in defence.
Elsewhere Aaron Ramsey and Francis Coquelin join Rosicky in midfield while Marouane Chamakh starts in a three-pronged attack with the Ivorian and Alex Oxlade-Chamberlain.
Olympiakos: Carroll; Maniatis, Machado, Conteras, Manolas; Torossidis, Fejsa, Diakite, Greco; Abdoun, Djebbour.
Subs: Megyeri, Ibagaza, Ioannnis, Fuster, Siovas, Pantelic, Mitroglou
Arsenal: Szczesny; Jenkinson, Squillaci, Vermaelen, Meade; Rosicky, Ramsey, Coquelin; Oxlade-Chamberlain, Chamakh, Gervinho.
Subs: Shea, Angha, Hajrovic, Monteiro, Arshavin, Ansah, Akpom #afc