Extend his contract, but if conte leaves (highly doubt) then I really think Marotta's faults will become more clear.
None expected some of his signings to turn out the way they did. I think a large factor of that has to be attributed to Conte.
Estigarribia - Was a nobody, till late in the season. I wish we kept him, honestly he would probably start over Asamoah in that LWB position
Barzagli - The system has really helped him become the player he is, oh and age. Wine does get better with wage afterall
Pirlo -

Excellent by Marotta to secure his signing. A gamble but every gamble has the potential for huge gains
Pepe - I'd consider him a success for what he did in the amount of time he was playing.
Whomelse have I missed? Either way Marotta has a knack for finding players who are capable of becoming much more. His negotiations skills are still in question for me though.