How do you determine whether a monster you polymorph into is capable of providing vocal components?
How for somatic components? So long as it has hands (or something akin) or opposable thumbs?
Since you can't make use of your equipment (which is melded into your body) there won't be any scrolls and wands to use.
But why couldn't you just put the important things aside (the wands and scrolls and potions and you material component spell pouch) and pick them up after transforming?
Verbal components are the easy part. If the monster entry lists any languages at all without a "cannot speak" note, then the monster can speak freely and thus can create the verbal components of spells.
Somatic components are trickier -- you have to make a judgment call in most cases.
It definitely is possible to prevent objects from merging with your form when you polymorph by dropping them before you do so. You can also put items that you might need into a Polymorphic Pouch to save you from even having to do that much.
Alright, thank you.