Marco Borriello struck the only of the game at the San Siro.
Ranieri remarked: "We could've created more in attack, but it wasn't easy against this very aggressive Milan side. They are an excellent squad and deserve to be top of the table.
"I was very satisfied with Adriano's performance, as he held up the ball and gave the team breathing space. You'll see he will become even more important to Roma in the new year."