Hi Cliff,
When I think of a blog roll its a list of links to other blogs that a user can put on their blog page. We don't currently have that built into the blog, but I've been thinking of adding an editable section in the same column with categories and archives where a user could put links or whatever they want.
It sounds like your definition of blog roll is a little different. You could easily create a "Blogs" page and then put a links module or even a plain html module with links to the different blogs but there is nothing to do this for you automatically. You can also use a Feed Manager to aggregate the blogs together by adding the feed of each blog to the Feed Manager, thats what I have done on the Community Blogs page. You can consume both external feeds and feeds from blogs within the site.
Hope it helps,
Joe