The reigning but retired world champion was asked by Spanish sports daily Marca about his thoughts on who should have replaced him in the Silver Arrows outfit.
"Ok, now that I'm a fan it's very easy to respond," Rosberg said.
"Everyone says Alonso and I say it too, because there would have been fireworks with Hamilton!
"As a fan it would be nice to see those sparks, but from the team side it couldn't have been and they found a great solution."
Rosberg considers that Mercedes were right however to poach Valtteri Bottas from Williams.
"Bottas is fast and he beat Massa three times in a way similar to Alonso did, and now he can do very well," said the German.
"Of course Hamilton will be at a very, very high level and it will be difficult to beat him, but I proved that it is possible."
The 31-year-old also said that Mercedes will get a run for its money from its rivals this year, and especially from Red Bull.
"Mercedes is the favourite, we are three times champion, although there are teams that are dangerous, like Red Bull," he said.
"Adrian Newey and new regulations are a combination that has been successful in the past, and I've also heard that he is back with the team as he was before. Red Bull will be the second force."