I've gotten 62 slayer now, trying to get 85 slayers to RS gold Abyssal Demons. I can't get on right now, and I want their stats while I have this free time in school to plan a set of gear, etc. to Abyssal Demons.
It's a great question and of interest to me as well. I low alch with the rings of the explorer due to the fact that it's free however it is limited to around 30 a day. I use the nats that I get to superheat ore. I get nats in drops as im fighting different monsters. Not my top priority to obtain runes, it's an element of luck for me. There is a list of monsters , as well as drop statistics should you decide to kill for a pile of Nats?
I train Slayer and often forget which of my critters had the greatest natural drops. . It is true that roaches do drop Nats, but unless fighting often, relying on this for production of nats is quite slow. However, on the bright side - the prices are cheap OSRS gold extremely low for certain items at the moment and runes are affordable to acquire if you have the gp needed to purchase an enormous stack.