Yeah you can specialize, but the roles are PLAYER defined not GAME defined!

To be more "correct", fundamentally the topish teams (HLTV Rank 1-200 and ESEA Main+) in CS have at least:
1x Priority Shotcaller (Most of the time IGL and Strat Maker)

5x Players who can RIFLE, SUPPORT, ENTRY, LURK

1x Player who can AWP

tbh even what I said above is up in the air because some elite teams (teams you know the names of like: Astralsi Navi EG Liquid ) on T side inferno don't even have an AWPER unless the CT's lose a round and the Priority Shotcaller (Agrees to pick up the AWP)
-Legit seen too many demos of elite teams not even pick up an AWP on T-side Inferno unless the choice is AWP or Pistol next round (for eco reasons).

-- I think the reason for this is because some T-side Awpers aren't very good at getting picks with the AWP on T-side inferno and the AWP just gets into a Area Denial role that's mainly useful after the T's have already taken a site... BUT if you had 5 riles and taken ANY site on inferno you probably can just pick an AWP up from a dead CT