"True randomness"
This is a meaningless phrase. What are you trying to say? For all intends and purposes, an honest dice roll is quite random.
I cannot fathom something happening without a cause.
I don't see the connection between this and randomness. Random events also have causes, but there is some property that is difficult to predict from their cause. It's hard to predict how a dice will roll. Heisenberg's uncertainty states that there is a fundamental limit to how accurately you can know the properties of quanta, so we can reason that fundamentally, there is a lot of randomness inherent to matter, as this limit prevents us from making completely accurate predictions and therefore at some level there is unpredictability inherent in the system.