The DU "police" are not to be feared. Usually, offenses don't end up tarnishing your school record or emptying your wallet. You might get a few slaps on the hand, unless the offense is something more serious, such as driving drunk or selling drugs on campus. RAs do their best to keep things quiet and relatively under control in the dorms, and as long as you don't blare your music too loud or get sloshed in your room, most likely you won't incur any serious run-ins.
Probably the biggest no-no on DU's campus is drinking in the dorms, considering DU markets itself as a dry campus. In their job description, RAs are required to inform the administration of any and all names of students caught drinking or doing drugs in the dorms, so be careful. Although you probably won't get suspended or expelled on the first account, mounting charges could equate to more serious penalties.