Former Roma man Osvaldo has been linked with a move back to Italy after being suspended by Southampton following a training ground bust-up.
The likes of Juventus and Inter Milan have been credited with an interest in Osvaldo, with the player reportedly keen on a move back to Serie A.
Marotta has admitted Osvaldo is on their list of targets, but that they must sell before they can buy anyone.
"We like Osvaldo and other clubs like him too," Marotta told Gazzetta dello Sport. "He is an excellent player, but before buying anyone we need to sell."
Marotta also revealed they will only sell unsettled forward Mirko Vucinic if he asks to leave Turin.
Vucinic has been linked with a move away from Juventus all month with a possible swap deal with Inter Milan's Fredy Guarin collapsing at the last minute.
A number of clubs are thought to be keen on Vucinic and Marotta insists the Montenegro international will only leave if he demands to quit.
"Vucinic? He will leave only if he asks to go," added Marotta.