While I haven't tried making scallion pancakes yet, I did make laminated parathas and fatayer, which are similar. My tips:
Add some water to the roux, it will steam and help the layers separate as well as adding moisture which will improve the dough itself. Same idea as applies to the use of butter in laminated pastries.
Griddle twice, first time on a lightly oiled surface, over high heat, this will help layer separation and dough texture. Don't try to color or crisp the dough, just make sure it's baked through. Then let the breads rest until ready to serve, at which time griddle them again over medium heat with some oil, until crisp. Similar concept as applies to french fries, and one I use for almost all breads I bake, as well as to pastries I want to be crisp, such as puff pastry and even muffins.
