Look at it this way.
I had 15 Compact Med Kits.
I split my items 1 stack of 10 items, and 5 stacks of 1 item.
I RE'ed my 5 single Compact Medkits individually and received a Green Goo for each one.
I RE'ed the stack of 10 Compact Medkits and received 10x Green Goo.
I would assume in this case that because you get the equal amount of RE'ed materials back from every item in the stack that you will indeed get that many rolls to learn a new recipe. I would assume again that RE'ing a stack of items gives you the same chances and materials as if you RE'ed each item individually.