You may want to look at the Samsung optical hub... A bit tricky to find though
Its a device thats not without its flaws... and you connect via wifi not otg (power supply required)
I bought one a couple of years ago (as i needed an external dvd writer for my laptop (works over usb for windows) and the android stuff is a bonus i suppose.
I've used it to watch dvds on my phone (twice), but mainly as a standard dvd writer on my laptop. can't recall ever writing dvd from my phone, so can't acutually confirm that works.
Anyway, here's a link, which at least gives you something to investigate...
don't think there are many other options. As most people would either use the cloud, or something like a usb stick and then transfer to a pc for writing