Gparted will not (AFAIK) let you modify partitions that are in use (e.g. root, boot, home...). It should also show which partitions are swap.
In grub, you can find which partition is the root for a particular distro by highlighting the disto name and pressing e. The line beginning with the word kernel should have "root=" followed by the root partition.
You could also try mounting the partitions:
mount /dev/sdaX /mnt
You can't mount swap, so this will help you find the swap partitions.