Roundabouts are the very last place where I would consider a bike lane to be a possible net win in safety. If the bike lane has priority at exits, then it will be constantly ignored, if it doesn't, then cyclists would be at the mercy of exciting drivers never forgetting to indicate, resulting in similar bloodshed. Besides being totally shitty towards cyclists who would then have to yield three times for going left at a crossroad-equivalent, at a very uncomfortable viewing angle and with permanent risk of un-indicated exits.