For those synced from iTunes, you will need to uncheck them in the iTunes sync settings for the iPad.
For those saved to albums from your camera roll, those are specific to that device, they may be on other devices via photo stream and if so they won't be deleted from other devices by deleting them from the camera roll on the phone. However if they aren't on other devices, they are your only copies, so be sure you want to delete them.
If they are in photo stream, if you delete them, they will be deleted everywhere, if you turn photo stream off on the phone instead, they won't get deleted everywhere but you won't be able to share new photos you take on your phone.
If they are in a shared stream, if you delete them, they will be deleted everywhere, if you turn shared streams off on the phone instead, they won't get deleted everywhere but you won't be able to share new photos you take on your phone via shared streams.