You do not have to adjust the declination on your compass when using an orienteering map. Orienteering maps have north-south lines that are oriented to magnetic north.
Some of RMOC's long-distance events may utilize USGS topo maps instead of standard orienteering maps. In that case, the Course Setter will usually overlay magnetic north lines onto the map. If that's not the case, then an announcement about declination will be made prior to the start of the event.