Obimom is correct. Roxicodone is just hydrocodone. However, hydrocodone is metabolized primarly in the liver, as are most pain medications. Suggest that they talk with their pharmacist about any medication they are considering, whether it's over-the-counter or prescription. Pharmacists have the best knowledge about how various medications work in the body and are usually very happy to answer your questions.
His best bet is going to be to look into forms of pain relief other than medication, such as acupuncture or a TENS unit. If his pain is severe enough, they might want to talk to his doctor about neurostimulation. Here is some information on these options:
Acupuncture: http://www.healthcentral.com/chronic-pain/alternative-pain-relief-255116-5.html
TENS unit: http://www.healthcentral.com/chronic-pain/treatment-36204-5.html
Neurostimulation: http://www.healthcentral.com/chronic-pain/neurostimulation-and-pain-pumps.html