Help with Radio's .root files

I was doing a period check of very large files on my computer, planning to backup or remove the largest ones to make some room, and I noticed that among the top five files, four of them were .root files used by Radio:

• aggregatorData.root (149 megs)
• weblogData.root (128 megs)
• manilaBloggerBridgeData.root (79 meg)
• Radio.root (31 meg)

Now, I know Radio.root is the guts of the program itself and I shouldn’t mess with it, and I know that weblogData.root contains the actual posts for my Mediajunkie blog and if I remove it they will be upstream-killed, so I’m not going to mess with that, for the time being, but I have questions about the other two.
First of all, is aggregratorData.root just a complete archive of everything I’ve ever gathered in my aggregrator (and/or not deleted)? If so, I don’t need it, don’t plan to search it, and would like to wipe it out, but I won’t do so until I know it won’t take the whole program down with it.
Secondly, why the heck is the manilaBloggerBridgeData.root file so freakin’ large? I’m not even using it anymore. Can I wipe this?