Did you read the link?
It does not take much thought to realize that a council convened hundreds of years after a persons death cannot have as it's main goal or purpose to condemn a dead man. It would have to be about something else. And what they could investigate would be people's current teachings and the writings of Origen. They obviously could not investigate Origen himself.
As I read online the mention of his name in that council, it was asking people to renounce beliefs based on a list of men including Origen, that and also a laundry list of things people were teaching and claiming authority from Origen's writings/teachings.
Without even looking to be sure, am pretty certain some (if not most) of the other people specifically mentioned along with Origen were also dead at the time. Major and even minor councils were big deals, dealing with real issues effecting the present day Church.
St Jerome's remarks indicate the first council's ( issues with Origen (399 AD dead 100+ already) were not doctrinal points.
And yes, it would be impossible for us now and probably very difficult if not impossible 100+ years after Origen's death to prove Origen actually held any of these positions. For all we know the "belief" of Origen being criticized could have been speculation, a misunderstanding or corruption by then living people of what Origen actually believed.
My whole point was that the council is condemning real, living people that held these beliefs and presumably were using the writings of a long dead Origen as a champion for their case. So the Church addressed as a response a condemnation Origen(isms).
It is really no different than Jeffcc or others using Origen today to support their own beliefs. My condemning those beliefs of Jeffcc as heretical does not prove Origen believed it or make Origen a heretic.
We should also keep in mind that at the time Origen wrote, many of the things he wrote about were not yet settled issues/doctrine within the Church. So while one could say in hindsight Origen was wrong about this or that, he cannot be called a heretic for something he could not know would be potentially considered heretical in the future.
As we have a two versions of his writings, one pro - one con, it is a safe bet that what he actually wrote is a mixture of both or somewhere in between.
More links to the councils on this issue
Origen died around 254 AD
Second one - 553 AD
http://www.newadvent.org/fathers/3812.htm
http://www.newadvent.org/cathen/04308b.htm
First one - the Alexandria council of 399
http://www.newadvent.org/cathen/01300a.htm
And note all of that in context of the article on Origen and Origenism.
http://www.newadvent.org/cathen/11306b.htm