I take Oxycontin 20mg 3X's daily, and Roxicodone 30mg 2X's daily.?

My ? is why does one make me REALLY tired. They are supposedly from the same family of narcotics, the oxycontin is a controlled release and the roxicodone is fast acting and stronger(30mg). However, when I take the Oxycontin 20mg/controlled release, it makes me extremely tired, but when I take the Roxicodone 30mg/ instant release, I feel as though I got a boost of energy. Does anyone maybe know why it makes me feel that way with one, than the other?