How can I see a list of users, who is assigned to what role, etc.?

If you are an Administrator, you have the ability to look up and (often) update/edit the information for the users in your system.  If you want to know who all is in your system, their roles, when they last logged in, etc. then you can export a list.

To do this, follow the steps found at the bottom of the article in Manage Users - For Admins.