I think that one has to embrace a rather open perspective in understanding the roots of Hinduism. It's difficult because the religion itself is quite old. Its roots can be traced back to a couple thousands of years B.C.E. This makes its roots very difficult to fully ascertain. I might suggest that one way that a person can begin to understand some of the basic roots within Hinduism is to begin the process of examining why some of the rituals done today have been done in the past. Assessing why some of those elements are practiced today and understood in both modern contexts and the context of the past can help individuals gain greater insight into the religion's roots and relevance. For example, why is Diwali celebrated? Why is the Ganges River so revered? These are just two examples of how modern practices can reveal a great deal of insight into the roots of the religion and its practice. Essentially, I think that the roots of the religion are so far embedded in human historical experience that one might be best set to understand why the constructs of the religion today are there, their meaning, and how important these constructions have been in the development of the religion. In this method of "working backwards," one might be able to gain greater understanding about its roots.