Well in comparison to your original habit, which was a pretty high dose, 1 30mg roxy is pretty small. Since you made it four days through the worst of it, taking 30mg may set you back, but I highly doubt your withdrawals will come back at the same intensity you felt the four days before re dosing. I would expect another couple days of moderate symptoms gradually fading into a bearable situation.
I don't blame you for taking that 30mg, I certainly would have as well if I had found it during a hardcore detox. I commend you for getting through the worst of it, as many people would NOT have been able to make it as far as you did. The acute withdrawal is very tough to get through cold turkey, so be proud of yourself that you made it that far. Most other people would have caved by day 2, myself included.
From here on out, it would be best to avoid taking any more oxycodone, and I am sure by next week you will be feeling more or less back to normal (physically atleast). After the acute withdrawal is done, the PAWS will still be there, which is often what leads people to relapse after getting through the physical sickness. The anxiety, insomnia, anhedonia, etc can be very hard to deal with.
It may be a good idea to speak with a doctor and see if he can prescribe some meds to help with the depression and insomnia and whatnot. Ideally you should avoid benzos, due to the addiction factor obviously. But in my opinion a small dose of benzos for a week or two shouldn't make you develop a physical dependency.
A big part of getting through the PAWS is learning how to cope with cravings. As much as some people hate it, AA/NA is a great place to go and has helped many people. You need to learn to love live without opiates. Staying active, exercising, heating healthy, spending time with friends/loved ones, and taking up some kind of hobby to occupy your time are all important things.
PAWS can last anywhere from weeks, to months, to years. It all depends on how much work you put in to get back to a normal lifestyle and learning to live without opiates. It is hard, but the ball is in your court. Sitting in your room moping about it will do nothing to make it go away, and potentially make the PAWS worse. This can consequently lead to relapse.
But overall, congratulations on making it this far, it takes some serious willpower to cold turkey a habit like that, and you should be proud of yourself for doing so. Do not beat yourself up for taking one roxi. You did great, just keep it up and stay strong.
Sorry for the novel, haha my meds have kicked in and i am feeling fantastic.
Cheers, good luck.