Juventus had to wait until the 81st minute for Cristiano Ronaldo to find the breakthrough against a spirited Frosinone. Cristiano Ronaldo struck in the final 10 minutes to put Champions League heartache behind him and set up Juventus’ hard-earned 2-0 victory over Frosinone on Sunday. Sent off against Valencia in midweek, the Portugal superstar gained a measure of redemption by sweeping home from close-range before substitute Federico Bernardeschi netted in stoppage time to maintain the champions’ perfect start in Serie A. It had looked as though Ronaldo would endure a no less frustrating affair than on his return to Spain,…