I think instead of just a flat overall rating for roles, it should look at the depth chart. Bledsoe was fine playing 20 minutes a game for the Clippers because he was playing behind CP3, and the Clippers had plenty of players that fit the SG role better than him such as Crawford, Billups, and Green. But he would certainly be unhappy if he was getting 20 minutes a game for the Suns this season, as he is either the first string PG or SG.
Green on the Clippers is another good example. He's probably going to get solid minutes for most teams in the league, but records DNP most games for the Clips because he's the third string SG, and plays whenever someone is injured. He's fine with his role on the Clippers, but he would usually complain in 2k.
I also feel like the role during contract negotiations should have more of an impact, as Green signed with the Clippers knowing he'll be a benchwarmer. If the Clippers were promising him a starting spot in 2k world when he signed, and he ends up as the third string SG, then he should be unhappy. But there should also be an personality trait that determines how willing a person is to sign for a smaller roles and how they react to not getting the role they were promised.

Comment