This debris comes from kids throwing things, such as glass bottles, onto the roof or tenants sub-contractors leaving miscellaneous garbage laying around. The problem with leaving this on the roof is that it gets stepped on and punctures the roofing membranes causing roof leaks.
You could have us check your roof while at the building doing a service call instead of making a special trip. While on the roof we could also check for cracks or tears in the membrane and clear debris from drains and overflow scuppers.
Please call our 763-551-0101 or send us an email at service@unitedoperations.com to schedule an inspection.