Q: How to delete from camera roll

I just synced hundreds of photos from iPhoto on my Mac (which doesn't have Lion yet and hence, no iCloud) to Photos on my new iPad.  Photo Stream is enabled but empty.  I would like to organize and delete lots of photos but seem to be stuck.  Can someone help me understand how this all works?  It doesn't seem like I can do much of anything with just the camera roll on the iPad.

Thanks!