Our current IIS setup as two applications running on different paths at (for example) http://server/sub-a and http://server/sub-b. I want to alias http://server/sub-a as root so that just going to http://server/ will bring up the contents of sub-a. The problem I face is that when I initially set up a ReverseProxy it negatively affected http://server/sub-b. I know this is a fairly common problem- how have you solved it? 99.9% of my experience is with Apache, so I feel a tad lost in the GUI world of IIS.
If it's a dedicated server then setup 2 separate sites pointing directly to the sub-a or sub-b folder. Set the specific bindings on each site.
If you need to share them under a single site then here's the solution to host multiple domains under one site
What you probably want to do is change the 'alias' of your application in IIS you would think you could do this by selecting the parent (usually 'Default') and then going 'View applications' and then 'advanced settings', but as posted here, the IIS manager front end does not allow you to make this sort of change, see this thread: http://stackoverflow.com/questions/5687057/renaming-applications-in-iis-7-0
However, as posted there, you can edit the configuration manually: http://learn.iis.net/page.aspx/150/understanding-sites-applications-and-virtual-directories-on-iis-7/#Configuration
... you would not be alone, if you thought this was one of less-than-helpful things about the IIS configuration utility.