When I did rollersets, I used a dime size amount of a creamy leave-in (NTM Silk Touch) on each section of hair before I rolled it up. I didn't apply it all over and then start rollersetting, I find that somewhat defeating the purpose of using a leave-in.
Now that I airdry, I have been applying the leave-in all over my hair (size of a chocolate hershey kiss). From now on, I will section in 4, detangle, then apply the leave-in to each section, then style my hair into a bun.
But if I use a liquid leave-in (like Motions Nourish) I section my hair in 2 sections or for sections and spray each section about 8 times before rolling it up or airdrying.
HTH!