Ultimately the driver didn't see the approaching traffic and pulled out on them. You saw the cyclist before the accident happened and so should the other driver.
Not necessarily. The OP entered the roundabout from a different road to the driver, and it was stated that the drivers view of traffic on the roundabout was compromised by a wall, the OP evidently had a better view of the roundabout and traffic from his entry point. It seems to be a case that the driver should have noticed the wall was obstructing his view and taken appropriate action such as stop at the give way line and do a proper look right. It sounds like the driver did an insufficient glance on approach at speed, didn't register the view obstructing wall, and his brain interpreted the lack of view of traffic on the roundabout as the roundabout being clear, so no need to stop. I can't see the cyclist being at fault here, whatever speed they were going at, they were on the roundabout at the time the driver entered it, the driver should have stopped and given way. It is not unlike what put me in hospital for seven weeks, the driver that hit me pulled onto the roundabout when I was directly in front of him. I suspect he was looking right waiting for a gap, then saw a gap (created by me), then went for it whilst still looking right instead of looking ahead.