The 26-year-old, who took his exams at Cardiff University while playing professional rugby, will graduate in the summer.
"My nickname amongst teammates has for some time been Doc, and I've always felt like a little bit of a fraud. It's nice that I'll finally be able to call myself a doctor," he told BBC Sport.
"It's been tough but it's been worth every second to achieve one of my main goals in life. I am very proud to have finally come to the end of my eight years at Cardiff University's School of Medicine.
"It's been a long, hard road and I would like to say a huge thanks to the school of medicine for allowing me to undertake my studies, part-time."
Roberts has made 53 appearances for his country.