Not possible with photos transferred from your computer via the iTunes sync process. The only way to delete photos from the iPad that were transferred from your computer via the iTunes sync process is via the iTunes sync process - except for erasing all data and settings from your iPad.
I have done the above suggested by you. My photos on my MacBook Pro are fine (have deleted ones I don't want), but when I sync, they are not deleted on the iPad. I sync through iTunes. I have over 2200 photos and they are taking up a lot of storage.