As with many hard seeds it is worth part grinding or roasting because otherwise they have a tendancy to 'pass' right through without the body receiving any benefit-rather a waste of energy collecting them in the first place. This is certainly the advice given by Gordon (Gandalf the Green) at Woodlore. Plantain seeds are just starting to ripen in my area and it is possible to collect quite large amounts quickly. The seed does require a modest winnowing to remove the 'chaff' but it's not important to completely clean them. I either grind them a little, add some water, press them out into 'biscuits' & bake them or mix them with other seeds & flours for breads & such like.