The role of the divine in the Hindu faith is no different than any other religion. The fundamental purpose is for individuals to recognize that within the divine, the supreme God- head, Brahman is present. This Brahman is "the unchanging reality amidst and beyond the world." The purpose of the divine is to remind the devotee of this condition and help move them closer to it. No different than any other religion, the purpose of the divine figures in the religion is to understand and embrace this condition of being while being a part of the mutable and temporal.
There is a standard and, sometimes skewed, view of the divine figures in Hinduism. This point of reference sees the divine trinity of the religion as separate and distinct. It sees Lord Brahma as the creator, Lord Vishnu as the preserver, and Lord Shiva as the destroyer. It is from here where the claim is made that the religion is polytheistic because there are different god- heads who are worshipped. However, an alternate point of view might be that the religion is monotheistic because it worships the Brahman. Each one of these figures are not separate from one another as if they are compartmentalized. Rather, they each represent the Brahman in different ways and work with one another in a fluid and distinct manner. (One can see a great deal of preservation in Lord Shiva and the scriptures speak of a large amount of destruction that can be wrought by Lord Vishnu.) From a fluid understanding of Brahman embraced by the major divine figures, one sees how the other aspects of Brahman such as Goddess Devi, Lord Ganesha and Lord Kartikeya all operate within another. From these divine representations, there are multiple representations and manifestations.
The purpose of the major divine figures is to help the individual in the modern setting understand how Brahman is to be appreciated in their lives. Consider the following analogy to help illuminate this condition. The lotus flower exists in filth and muck. Yet, as it emerges towards the sunlight and grows, it does not retain any of this filth. It is mired in filth, but none of it sticks to it as it emerges into being. Hinduism sees the purpose of the divine as a reminder to the individual of what Brahman is. The individual is the lotus flower that grows towards the heavens, moving closer towards the realization and understanding of Brahman in the "muck" of this life without enabling the contents of this birth to stick to the individual. The divine figures in the religion are the reminders of this Brahman and its need to appropriate this spirit into this being as the true and transcendent essence of being.