According to Catholicism, do Gabriel, Michael and Rafael still have the option of turning away from God? On the assumption that Satan was once in fellowship with God. Do Gabriel, Michael and Rafael (or any angel) still have the option of turning away from God?

If so, is the sainthood of a human greater than an Angel? 

Because if a human dies and goes to heaven, their fellowship with God is eternal and perfect so the option of turning away from him ceases to exist.
If you take St. Thomas's answer as good 'nuff.  He has about 3 articles that hint at an answer in the Summa of which, I think this is the most concise:


  I answer that, The beatified angels cannot sin. The reason for this is, because their beatitude consists in seeing God through His essence. Now, God's essence is the very essence of goodness. Consequently the angel beholding God is disposed towards God in the same way as anyone else not seeing God is to the common form of goodness. Now it is impossible for any man either to will or to do anything except aiming at what is good; or for him to wish to turn away from good precisely as such. Therefore the beatified angel can neither will nor act, except as aiming towards God. Now whoever wills or acts in this manner cannot sin. Consequently the beatified angel cannot sin. 
  
  http://www.newadvent.org/summa/1062.htm#article8


So, like Mother Mary,  in Heaven, an angel would follow intellect, not passions, and therefore never turn towards sin.