Snow load is typically carefully considered during construction of a new building. Insulation thickness and placement of roof top units can affect the structural bracing of the roof deck.
When a roof is replaced, or new penetrations are added it's uncommon to consider what the new components will mean for snow loads. It's very important to monitor snow loads through the entire life of the roof - you don't want to be on the news. Snow removal is the simple and cost-effective solution.