Here's some signs to tell u if he is on roxy's or any other opiate opoids. His eyes will tell all! They will be very glassy and shinny. His pupils will be the size of a pin poin or needle, very tiny! He may itch alot and not sit still. Be in a very good mood then get really irretated and mad over little things. Hope this helps you tell rather or not he's still using.
A for sure is a drug test. Otherwise, If he seems tired and lethargic, his eyes and head are nodding off at times. Coming from experience it's easy to hide if you're not doing a lot. If you want to know for sure, get a drug test and make him take it. I'd advise in a bedroom or something so he doesnt try to put water in to dillute it.