It sounds like you want to implement your own version of the ASP.NET Web Site Administration Tool (WSAT) for use "inside of" your own website.
The walk-through that you link to is okay, however, it doesn't walk through creating anything that is particularly generic and can be simply "dropped in" to an existing web site.
I'd suggest looking at this tutorial:
Rolling Your Own Website Administration Tool
as a way of creating your own set of pages specifically for user/role/membership management. You can even download the code for the article if you don't want to re-type it all out yourself. Unfortunately, the code for this tool and in this article is in C#, however, the code is not especially complex and should be able to be easily converted to VB.NET using one of the many available code converter tools.
There is also this tutorial:
Users and Roles On The Production Website
which is VB-specific and should help with building your own WSAT-like tool.
Some time ago, on the CodePlex site, there was an ASP.NET WSAT Starter Kit project that also served the same purpose (and arguably improved on the "default" WSAT considerably), however, that project unfortunately no longer exists. After some searching however, it appears as though the code for this tool is still available, so you could perhaps take a look at that tool also (the code is in VB).
You can find that here:
ASP.Net WSAT (Web Site Administration) Starter Kit. What happened?
(check the very last post at the bottom of the page).