Peter Vok was born in Český Krumlov, the son of Jošt III of Rosenberg, then head of the house of Rožmberk, and his wife Anna of Rogendorf. Fourteen days after Peter's birth, his father died. Peter came under the guardianship of first his uncle Petr V of Rosenberg and later Albrecht of Gutnštejn, Oldřich Holický of Sternberg and Jeroným Schlick.
He received his early education at home in the castle at Český Krumlov. Even as he reached adulthood, Peter lived in the shadow of his older brother William. While William was a life-long Catholic, Peter sympathised with Utraquism and eventually joined the Unity of the Brethren. William died in 1592, and Peter inherited the Rosenberg holdings.
Aged forty, Peter married the much younger Kateřina of Ludanice. Initially an idyllic marriage, with the young Kateřina appreciating the attention paid her by her aging husband, the union began to break down, in part because of Kateřina's worsening mental illness. The couple had no children, and the Rosenberg line ended with Peter Vok. He died, aged 72, in Třeboň in 1611 and was buried in a Rosenberg tomb in the Vyšší Brod Monastery. Shortly after Peter's death, his nephew Jan Zrinský of Seryn also died, and as such the whole Rosenberg dominions passed to the Švamberk family.