Social and Weekend runs can be set up at any time, by any member. Simply 'Add a social & weekend run' to the calendar and it will be displayed for all club members to see. You should find the Sunday Morning runs advertised here on the calendar, but if they don't suit your time or pace, why not suggest another run here and on the RPAC Facebook Group.
If you see a run that you would like to join, it would be helpful to let the person who suggested it know. You can do this by using the 'Like' button on the Facebook Group. They are not official events, and all members participate at heir own risk.