Hi there! I'm also a long time reader, but only just recently made an account.
I'm a local Indonesian and have been to several rave festival in Jakarta in the past two years. I did not go to DWP last year tho, but am planning to go this year although I doubt that I would be rolling.
From what I see, Jakarta is tightening up its drug laws and enforcements but it is nowhere as strict as the Philippines yet. In my last rave this past August I noticed several people who I am sure are high on E. There were even people in my group (that I just got to know – they were my friends of friends of my GF) who brought a joint or two and offered me a puff. I declined because my GF was very much against all kinds of drugs. But from what I see it was pretty potent stuff and everybody was dancing merrily through the night.
As to rolling - just be sure that you can control yourself. There was this dude who was just soo00o obviously out of whack. He was aggressively pushing and shouting. And he was drinking water, uncontrollably shaking his head. Too much. Too obvious. But even then, no security took him out or whatever, we just gave him space and his friends keep apologizing to the people around and carrying him back into his group.
However, I do think you will have problem getting access to whatever is your choice of drug. Speaking from experience it used to be so easy – you just go to one of "those clubs" in Kota area, and ask the waiter. But on my last try in June it was extremely hard to get access. The waiters no longer simply sell you the stuff because they are scared of police raids. They only sell to regulars, which means harder access for people like me who only wants to roll once in a blue moon. Well anyway, that was my experience in June. Perhaps in future it would be back to normal, but perhaps even stricter.
So, the conclusion :
Safe to roll? Yes, but make sure you can control yourself and don't stand out from the crowd.
Easy to buy drugs? Nowhere as easy as it used to.
Hope you have a blast. Enjoy your trip and stay safe!