Rosberg was in Barcelona on Wednesday just three months after his shock retirement to witness the third day of pre-season testing.
Rosberg was in Barcelona on Wednesday just three months after his shock retirement to witness the third day of pre-season testing as his replacement at Mercedes, Valtteri Bottas, set the fastest time.
"There is such a massive hype at the moment so I wanted to see it first hand, as well as see the new cars," Rosberg told F1.com
"They look absolutely monstrous -- very, very aggressive -- and everybody is excited and that is great to see.
"The drivers are loving it and I think this year they will be proper gladiators out there with these cars because the cars will take them to their physical limits.
"We might even see drivers losing race wins because of just being game over physically and that's what we need."
Rosberg's former teammate and world championship rival for the past three seasons Lewis Hamilton admitted on Tuesday to having "bruises and bumps where I've never really had them before" after just half a day of testing.
Despite changes in regulations that make for wider and more powerful cars, Mercedes look again to have an edge over their rivals with Bottas and Hamilton suffering no reliability problems through the first three days and both clocking fastest times.
However, Rosberg insisted he had no regrets over his shock decision to retire at just 31.
"I expected the team to be the best this year because the team is awesome," he added.
"For sure it looks like they've done a good car, but that's no surprise."