I've read reports indicating the mass murderer Dylann Roof "may" have been on Suboxone. He may not have been, but let's say he was or is on Suboxone. If so, to my knowledge:
1. Suboxone is primarily used to treat people with opioid addiction. Addiction to opioids like morphine or heroin. Basically, Suboxone reduces the craving for opioids and it reduces withdrawal symptoms.
2. Suboxone is a fairly mild and safe drug (unlike say methadone which is a standard treatment for addiction to opioids like heroin and which needs to be very closely monitored).
In fact, Suboxone isn't generally even used as initial treatment to come off of opioid addiction, although perhaps it can be, but rather it's normally used to maintain the treatment once the initial treatment is successful.
Not to mention Suboxone isn't strong or powerful enough to be used in people who need high maintenance doses. It's generally used in people who require mild to maybe moderate maintenance doses.
3. I think there are basically two possibilities: the Suboxone was working, or the Suboxone wasn't working.
a. If the Suboxone was working, then I can't see how Roof's use of Suboxone would make him less culpable. If anything, if the Suboxone is working, then Dylann should feel more settled or stable in mind. More like a normal person.
b. If the Suboxone wasn't working, or not working well enough, then there could be side effects. However, even still, the side effects are not normally mind-altering effects.
The main side effects are mainly constipation, upset stomach, nausea and vomiting, lower blood pressure, headaches, dizziness, sleepiness or drowsiness, mild agitation.
Also, Suboxone itself can be addictive, but certainly far less addictive than the opioids it's meant to counter (e.g. morphine, heroin).
4. However, Suboxone is not a street drug, I don't think. Junkies would prefer something much stronger like heroin. Suboxone is relatively expensive for the average person (was Roof insured?) and requires a prescription. How would Roof have acquired Suboxone in the first place?