The German topped the leaderboard in Friday’s opening practice at the Circuit de Barcelona-Catalunya with a 1m 26.828, a tenth above his Mercedes team-mate.
A strong Ferrari showing had Sebastian Vettel and Kimi Raikkonen third and fourth behind the Mercedes duo, with the Toro Rossos behind, for the delight of home fans, with Carlos Sainz fifth.
Ferrari are believed to have tested up to 16 new parts on their car, as we saw most cars with upgrades, and of course the new McLaren paint-job on track. McLaren, however, did struggle spite its new livery and were a modest 15th and 16th.
Meanwhile, it was a good session for the test drivers, as Jolyon Palmer really impressed for Lotus, Raffaele Marciello was right behind Palmer for Sauber in 12th, and Susie Wolff was less than a second off Felipe Massa for Williams.
Many difficulties on track this morning session, Hamilton complained from oversteer, Vettel went off at turns 1 and 10, but the luckiest was Rosberg however, as he escaped a sporting penalty after making an illegal entry to the pits, and received a reprimand.
The top ten in the first practice:
1. Rosberg — 1:26.828
2. Hamilton — +0.07s
3. Vettel — +0.978s
4. Raikkonen — +1.004s
5. Sainz — +1.304s
6. Verstappen — +1.701s
7. Kvyat — +1.957s
8. Massa — +2.003s
9. Ricciardo — +2.247s
10. Nasr — +2.312s