****Warning*****
Something I just learned after I tried to remove a Bamboo SP Calendar Solution from our farm. It changes webconfig to reference new/updated Telerik command/extension.
The removal of their solution cripples your SharePoint rendering all sites outside of Central Admin unreachable.
Solution is to re-install their core wsp from trail solution.
If you wish to remove completely without crippling your SP check out their write up:
http://community.bamboosolutions.com/blogs/sharepoint-2010/archive/2012/08/23/how-to-remove-a-web-config-modification-using-powershell.aspx
http://store.bamboosolutions.com/KB/article.aspx?id=12486&query=Telerik.Web.UI