Thanks for your query.
As you are taking Roxicodone
hydrochloride),an opioid analgesic
. It will test positive for heroin in urine and it is not false positive, in fact it is true positive. Opiod derived drugs undergo metabolism
and rise morphine levels in blood and excrete through urine giving positive results. However some antibiotics may give false positive results for heroine.
Now relax, and visit your doctor which is scheduled.
Hope it helps.