It clinched a domestic double for coach Luciano Spalletti in his first season in St Petersburg after the Italian led the big-spending club, backed by Russian energy giant Gazprom, to victory in the Russian Cup in May.
Zenit, who missed a chance to seal the title in midweek when they suffered a 3-1 home defeat by CSKA Moscow, had to wait until five minutes before halftime to go ahead against Rostov.
"There was a lot of pressure (to win) on the team and it was like that for the last four months - we had a big lead and people thought we should win the title almost any day," the Italian told Russian television NTV.
"But nobody would just give us the points. We had to fight in every match and I would like to give special thanks to my players, our (Gazprom) boss (Alexei Miller) and all our fans and this beautiful city (of St Petersburg)."
It was Zenit's third league title and the second since 2007 when they were led by Dutchman Dick Advocaat.
