Depending on why you need to analyze the dependencies, in my usecase, I'm receiving xsd files from different sources, usually as zip file of many schema files. To open it in the schema authoring tool, I need to know root level file that include all others (in some cases there maybe few such files). For that reason and others, I wrote (freeware) Xsd Explorer utility, it can open schema directly from zip file or directory. It is mainly xsd visualization tool, but if you need to know root level files, it is specified in the log view