We went through a lot of bullshit with the OPs. I didn't really like them, because I was mad about the fact that I'd never see a real OC again at the time (I did end up getting two more, another story

). We only got them when nothing else was around because they were really cheap compared to the old school ones.
First method was the microwave/freezer one, which I never really cared for. Nasally the rush was nothing like the old ones, but again, good enough for what I was paying.
After that we did the "toaster oven" method which worked best for nasal ROA imo. However, like the microwave you gotta be very careful that you don't get the stuff too hot and you will lose some in the process. Also, I don't like the idea of snorting that stuff at all, but when you're chasing...
Last method was the soda over night method, which is the way to go if you ask me. I don't think you lose much, it is easy to do, and finally you can get away with it when you don't want everyone else in the house knowing what you're up to. The only downside is you have to wait a night or so before you can get well.
All that said, the OPs aren't good for you even when taken as directed imho. I do not trust the time release or the fact that it contains a known carcinogen. At the end of my use I only got these to combat W/D, and I would simply eat them. That was the one advantage of it for me, because it would keep W/D away for 24 hours if I took enough of it.
Switching topics to roxicodone;
When I was doing roxi I found a split between oral and nasal to be the best. I would hold 15mg under my tongue until it was mush, then swallow it about 5 minutes later. After that was out of the way, I'd rail 15mg. This provided the rush I was looking for combined with slightly longer duration. Using this method I could watch my pupils go pin-point in a mirror within a few minutes. They would stay that way for the better part of 8-10 hours.
HR note: don't assume 30mg of oxycodone is okay for you just because I started at that dose with roxicodone. By that time I already had a bit of a tolerance. For some people 30mg would barley take away dope sickness, for a naive user it might be more than they can handle.
BTW as someone that's done both roxi and old school OCs I have to say the rush of roxi is nothing like OC. Roxi is basically just like taking a regular old percocet with out all that APAP in it. That's why I fell in love with them, because I could snort it without having to worry about 325-500mg of APAP going up my nose with each crushed pill.
If you're looking to replicate the effects of an old school OC with pain medication the only thing close to it is a bit of Opana ER mixed with Roxicodone done nasally. That will provide a similar rush/high of old school OC, but it won't kick in as fast nor will it feel the same. Opana by itself is strong as is, but it lacks the euphoria of oxycodone IME which is why Roxi was added to the mix in my circles.
Keep in mind mixing Opana ER and Roxicodone and railing it isn't exactly a bright idea. You have to be very careful with it.