added error messaging to roles controller
added error messaging to roles controller

DigitalCurationCentre/roadmap,DMPRoadmap/roadmap,briri/roadmap,CDLUC3/roadmap,DigitalCurationCentre/roadmap,CDLUC3/roadmap,CDLUC3/roadmap,DMPRoadmap/roadmap,CDLUC3/roadmap,briri/roadmap,CDLUC3/dmptool,DigitalCurationCentre/roadmap,briri/roadmap,CDLUC3/dmptool,CDLUC3/dmptool,DMPRoadmap/roadmap,CDLUC3/dmptool