So what we do know is that the humans didn't originate on Roshar. Humans are the voidbringers since they brought ODIUM (the one who sucks in emotions or enhances them) to Roshar.
What I am unsure about is if HONOR and CULTIVATION were on Roshar prior to humans arriving. If so, I have a few thoughts and a possible theory.
I think that it is possible that the heralds (not heralds at the time of leaving) and other humans escaped the tranquill hills (or wherever they are from) to avoid the destruction that they brought upon themselves with ODIUM's influence. I am making the assumption that they didn't think ODIUM would or could follow.
The original Parshendi didn't have forms of power at the time the original humans arrived. They had the old rythms but didn't have any surgebinding capabilities at the time.
When ODIUM showed up, he managed to start turning the Parshendi on humans and themselves. Since the humans were aware of this, a deal was made with HONOR to help protect all of Roshar to include the Parshendi from ODIUM and these forms of power. This is where the heralds were given the honor blades and dawnshards (possibly) and were charged with protecting all life and to stop ODIUM.
This started the Desolations and the spren learned to mimic the forms of power that ODIUM gave to the parshendi and what HONOR gave to the heralds which birthed the knight radiants.
The reason I think this is because the humans on their original world were destroyed by surgebinding. If HONOR (who we associate with giving surgebinding abilities) wasn't there and ODIUM was, than how did humans have the ability to surgebind to begin with. And how did the humans end up with HONOR and some of the Parshendi end up with ODIUM?
Also to help with this, towards the end of OB, Dalinar states that only 9 of the orders are present. I think there was ten orders present and the tenth one was Venli. A Parshendi who is coming back to HONOR since she now has a spren.
What do you guys think?