If I wear a condom while receiving oral sex, and the girl licks my scrotum / testicles, am I at risk of any STDs?
If so, is there anything I can do to protect my scrotum area?
You can get Genital Herpes from someone licking your scrotum and there is no protection from Genital Herpes with condoms anyway as they don't cover the scrotum.
With oral sex, the risk is only there for you if the person giving oral sex has a cold sore and the risk is only there for your partner if you have Genital Herpes.