I rode 99 from Matera to Altamura in May 2012. Pleasant rolling hills. While mostly straight, the road has just enough high speed sweepers to keep things entertaining.
Right then the roads are right from Genzano on the 169 towards Oppido
From Oppido head east on the 96bis towards Altamura.
From altamura take the 99 south to Matera.
In Matera enjoy the fantastic scenery (It's where they filmed Mel Gibson's
"The Passion of Christ") and make sure you visit the Sassi (caves).