Questions about cetasikas 1) How are cetasikas expressed? Could they be expressed as how the mind is orientated, thus influencing how, when, and what cittas arise?

2) Do cetasikas therefore play any indirect role in the patticasamuppada process (dependent origination, did I spell the Pali right), say, for example, by governing what vēdana arises in response to contact?
I have personally never studied 'cetasikas' but have studied Paticcasamuppada in detail. 

Paticcasamuppada explains the 12 conditions (paccaya) rather than causes (hetu) that condition the origination or generation of psychological suffering (sorrow, lamentation, pain, grief &amp; despair). 

Therefore, it is important to distinguish between 'generic vedana' arising at contact (such as vedana experienced by a fully enlightened arahant that has attained Nibbana) and 'ignorant vedana' arising in paticcasamuppada, which occurs due to ignorance. 

Since 'contact' is a 'cetasika' (per Wikipedia), all vedana is a response to the citasika of contact. 

However, in paticcasamuppada, every one of the 12 conditions (and their sub-constituents, which total at least 54) arise due to the cetasika of ignorance/wrong-view/delusion, as described in the quote below: 


  To an uninstructed, run-of-the-mill person, touched by feeling that which is felt born of contact with ignorance, craving arises. That fabrication of 'self'
  is born of that. And that fabrication is inconstant, fabricated,
  dependently co-arisen. That craving... That feeling... That contact...
  That ignorance is inconstant, fabricated, dependently co-arisen.
  
  Parileyyaka Sutta