The 27-year-old center back comes in from the Portuguese champions to boost the numbers in the Partenopei back-line ahead of their Serie A run-in.
And Rolando, who passed a medical on Thursday morning before being presented with the sky blue shirt, has told the club's official website that he cannot wait to get started.
"I am very happy to be here," he said. "I wanted to join Napoli because they are a great club with many top players.
"I have spoken before about the passion of the fans, and I can't wait to play at the San Paolo."
Rolando joins Croatian midfielder Josip Radosevic as a new boy in Naples. The 18-year-old has also arrived on a loan deal until the end of the season from Hajduk Split, while Bruno Uvini has left the club for Siena on a short-term arrangement.