"I am so tired, I gave it 100%," he said. "I struggled a lot but I had fun on the bike. I rode to the limit and this gave me the present that is winning at Jerez, which was one of my dreams."
Lorenzo said he was amazed to have stayed out in the lead for so long and despite missing out on victory, he was happy with his day's work.
"I was surprised to be up there but in the last 10 laps I saw Jorge was coming five-tenths of a second quicker than me, and I thought 'this will be tight'.
Lorenzo 'amazed' with Spanish MotoGP win
"I tried to hold him back but it wasn't possible - second place by half a lap is not the best, but compared to Qatar (where he came seventh) it's good."
Rossi, who won the season opening race in Qatar, had come into the weekend with a shoulder injury, and said he was satisfied with his day's work under the circumstances.
"I had an injury, and in practice we struggled a lot, so this point is good - I did the best I could.
"I had a great start and tried to stay with Dani but didn't have enough. I always pushed but I was not at 100% today - and I don't want to create a problem with the Spanish party," he joked.
The Moto2 race had to be restarted after a mass crash on lap two, caused by oil on the track.
Lorenzo jumps in lake after MotoGP win
When the race proper began, Spain's Toni Elias was first home, ahead of Japan's Shoya Tomizawa and Thomas Luthi of Switzerland.
And to complete a Spanish hat-trick of success, Pol Espargaro won the 125cc race, ahead of compatriots Nico Terol and Esteve Rabat.
Great Britain's Bradley Smith came fourth.
Spanish MotoGP race result:
1 J Lorenzo (Sp) Fiat Yamaha 45mins 17.538secs 2 D Pedrosa (Sp) Repsol Honda 45:18.081 3 V Rossi (It) Fiat Yamaha 45:18.428 4 N Hayden (US) Ducati 45:26.553 5 C Stoner (Aus) Ducati 45:27.572 6 A Dovizioso (It) Repsol Honda 45:40.682 7 M Kallio (Fin) Pramac Racing 45:52.027 8 M Melandri (It) San Carlo Gresini Honda 45:52.225 9 R de Puniet (Fr) Honda 45:53.698 10 A Bautista (Sp) Suzuki 45:54.329 11 M Simoncelli (It) San Carlo Honda Gresini 45:54.693 12 C Edwards (US) Tech 3 Yamaha 45:55.798 13 H Barbera (Sp) Aspa Ducati 45:55.909 14 H Aoyama (Jpn) Honda 46:19.590 15 A Espargaro (Sp) Pramac Racing @ 3 laps
1 J Lorenzo (Sp) Yamaha 45 2 V Rossi (It) Yamaha 41 3 D Pedrosa (Sp) Honda 29 4 A Dovizioso (It) Honda 26 5 N Hayden (US) Ducati 26 6 R de Puniet (Fr) Honda 17 7 C Edwards (US) Yamaha 12 8 C Stoner (Aus) Ducati 11 9 B Spies (Aus) Yamaha 11 10 M Melandri (It) Honda 11 11 M Simoncelli (It) Honda 10 12 M Kallio (Fin) Ducati 9 13 H Aoyama (Jpn) Honda 8 14 L Capirossi (It) Suzuki 7 15 H Barbera (Sp) Ducati 7 16 A Bautista (Sp) Suzuki 6 17 A Espargaro (Sp) Ducati 1
Moto2 race result:
1 T Elias (Spn) Gresini 29:58.726 2 S Tomizawa (Jpn) Technomag 29:58.916 3 T Luthi (Swi) Interwetten 29:58.987
Moto2 championship standings:
1 S Tomizawa (Jpn) Suter 45 2 T Elias (Spn) Gresini 38 3 T Luthi (Swi) Interwetten 25
125 cc race result:
1 P Espargaro (Spn) Derbi 41mins 36.146secs 2 N Terol (Spn) Aprilia 41:38.032 3 E Rabat (Spn) Aprilia 41:51.326 4 B Smith (GB) Aprilia 41:53.256
125cc championship standings:
1 N Terol (Spn) Aprilia 45 points 2 P Espargaro (Spn) Derbi 38 3 E Rabat (Spn) Aprilia 25 4 B Smith (GB) Aprilia 21 5 E Vazquez (Spn) Derbi 20
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