It's easy to say that everyone had to drive within their tyres, but Rosberg was not the one who set the pace.
He led the race comfortably and he let the guy who was following him set the pace - whether it was his team-mate Lewis Hamilton or Red Bull's Sebastian Vettel - and Rosberg did enough to be ahead.
Nico Rosberg -
Sebastian Vettel -
Mark Webber -
Lewis Hamilton -
Adrian Sutil -
It was clever thinking in today's circumstances. None of the teams knew whether they would make it all the way on a one-stop strategy and all a driver can do is drive the car he has.
The one thing Mercedes need to look at is the way they handled the first safety car period.
When Felipe Massa crashed, the two drivers were at the Swimming Pool but they did not come in.
It was a big accident and the chances of a safety car were very high. But instead they went for another lap and got caught up in the safety car - you have to slow down to a certain pace once it is deployed.
That cost Hamilton second place to the Red Bulls and could have cost Rosberg the win.
They compounded that by the team letting Hamilton drop back by 10 seconds from Rosberg before he pitted. You only need a three-second gap to do a pit stop. So neither the driver nor the team should have let that happen.
CAN MERCEDES KEEP IT GOING?
Mercedes had the pace in Monaco. Will it carry through? I think it will.
They made some good modifications to their car for Monaco, changing the way the rear bodywork uses the exhaust gases.
All the top teams have exhausts that create rear downforce. If yours works less well, then you get more wheel spin. That overheats the rear tyres, which is what has been happening with the Mercedes.
But they have done a lot of detail work around that exhaust system which looks decent stuff, as well as tweaking the brake ducts to keep the brake heat out of the rear tyres. That will help a lot.
Rosberg was in good shape with his tyres all the way and that is a major turnaround from
the Spanish Grand Prix
two weeks previously.
DID CONTROVERSIAL TYRE TEST MAKE THE DIFFERENCE?
Were Mercedes' tyre-wear improvements a direct result of the controversial three-day tyre test the team did in Barcelona after the race?
It almost certainly clarified it for them.
Formula 1 tyre test row explained
I struggle to find a regulation that says that test was legal, but obviously they think it's OK, so we will have to find out what comes of that now it has been
referred to governing body the FIA.
There is no mid-season testing and for anyone who has a problem - as Mercedes did with their tyre usage - any testing, especially 1,000km over three days, is a fantastic way of finding a solution.
That is not a lot of running spread over three days, so there would be plenty of time for set-up changes along the way.
The only way I can see of making it fair is to allow everyone else to have three days of testing after the Canadian Grand Prix but make Mercedes stay away.
A POOR WEEKEND FOR FERRARI
Heading into Monaco, Ferrari were one of the favourites. They had a car that should have been good there and Fernando Alonso is fantastic around that track.
The car looked great out on the circuit in Thursday's practice, even if the long-run lap time was not quite there.
But in the race Alonso went backwards in the first stint on the super-soft tyres. Then they went onto the soft tyre and looked pretty competitive.
So I was surprised when they went back onto the super-softs for the restart after the red-flag period, especially as they had new softs available.
Monaco GP: Maldonado crash brings out red flags
Seventh was a poor result, even allowing for the problems Alonso had with his car with a plastic bag blocking his front wing and debris under the floor, both of which cost him downforce.
At every other race this year, Ferrari have been strong. This was the first one at which they have been uncompetitive. And that's a bit worrying because Monaco should be their track.
As for Felipe Massa, I have no idea why he would crash like he did at Sainte Devote once, let alone twice.
There is something strange going on there and they need to look at that closely because having accidents he can't explain could easily frustrate him.
GROSJEAN BACK TO THE BAD OLD DAYS
Lotus's Romain Grosjean had four accidents in three days and all of them were completely unnecessary.
The car is good - it's consistent on the tyres and works very well - but he is wasting it.
If he is not going to grab points, what's the point of it all? He was very quick, but he made three or four steps backwards instead of going forwards.
There are two types of driver I used to work with. One would go past you on the pit wall into the last lap and as far as you were concerned that was job done; Grosjean would be the other type - the one you'd be peering round the corner to see if he came back again.
Gary Anderson was talking to BBC Sport's Andrew Benson.
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