I’d keep repeating to EVERYONE who questions you that you were just getting a frisbee off the roof.
Them - “You know it’s tresspassing blah blah blah”
You - “I was just getting my Frisbee”
Them - " You can be charged with disorderly conduct"
You - " I was just getting my Frisbee"
Them - " If other students saw you up there they may try to go up as well"
You - etc etc
It sounds silly, but you may actually instill how retarded they are for jumping leaps and bounds over you getting your Frisbee. You may also want to go around telling everyone you know and more about it. There’s nothing more influential to change ones mind than the heat of the media.
Don’t ask how I know this.